BKCJ-0502 - 12/14 tooth, XD-15 Ceramic Hybrid Bearing, Machined Delrin Derailleur Pulleys for 12 speed SRAM Eagle Derailleurs (5mm bolt hole)The ultimate upgrade pulley. Guaranteed to last forever against corrosionPrecision machined Delrin¬Æ Derailleur pulleys featuring XD-15 Ceramic-Hybrid, radial bearings for enhanced shifting performance and longevity. Designed and manufactured for performance, these pulleys feature CN (tight clearance) bearings in the upper pulley to maximize shifting accuracy and C4 (loose clearance) bearings in the lower pulley to allow for chain-line movement.500 AF Delrin¬Æ pulley material features a high mechanical tensile strength and rigidity, natural lubricity, high resistance to moisture, caustic chemicals and UV makes these pulleys highly durable, rigid and very smooth. Delrin also machines very cleanly and precisely. The in therent lubricative qualities of this Teflon¬Æ infused material greatly reduces friction when it interfaces with the bicycle chain. When compared to other pulley materials, 500 AF Delrin¬Æ with Teflon¬Æ, offers significantly less drag than pulleys machined from aluminum or titanium.An Enduro Bearings exclusive, our XD-15 Ceramic-Hybrid bearings combine corrosion-proof, cryogenically treated nitrogen steel races with Silicon Nitride Grade 3 ceramic balls in a proprietary process that results in the ultimate high performance bearing setup. The deep-groove design raceways allow for maximum sized Grade 3 Silicon Nitride ceramic balls for for increased contact area and improved performance and longevity. 90% fill Kluber NBU52 grease only runs better and smoother with time and is highly resistant to being washed out. It is engineered to stick to the balls and continually be pulled back into the ball path where it is needed.The 12 tooth upper pulley/14 tooth lower pulley set 5mm bolt-holes is designed as an upgrade for SRAM 12 speed cable-actuated Eagle derailleurs (includes XD-15 cable idler pulley.)Enduro Derailleur Pulleys are available in a number of configurations and performance levels, starting with Ceramic-Hybrid, Black-Oxide treated Zero Ceramic as a step up, and XD-15 Ceramic-Hybrid at the top of the line. All are proudly precision manufactured in the USA.Enduro Item Code: BKCJ-0502

BKCJ-0501 - 12/14 tooth, XD-15 Ceramic Hybrid Bearing, Machined Delrin Derailleur Pulleys for 12 speed SRAM Eagle Derailleurs (5mm bolt hole)The ultimate upgrade pulley. Guaranteed to last forever against corrosionPrecision machined Delrin¬Æ Derailleur pulleys featuring XD-15 Ceramic-Hybrid, radial bearings for enhanced shifting performance and longevity. Designed and manufactured for performance, these pulleys feature CN (tight clearance) bearings in the upper pulley to maximize shifting accuracy and C4 (loose clearance) bearings in the lower pulley to allow for chain-line movement.500 AF Delrin¬Æ pulley material features a high mechanical tensile strength and rigidity, natural lubricity, high resistance to moisture, caustic chemicals and UV makes these pulleys highly durable, rigid and very smooth. Delrin also machines very cleanly and precisely. The in therent lubricative qualities of this Teflon¬Æ infused material greatly reduces friction when it interfaces with the bicycle chain. When compared to other pulley materials, 500 AF Delrin¬Æ with Teflon¬Æ, offers significantly less drag than pulleys machined from aluminum or titanium.An Enduro Bearings exclusive, our XD-15 Ceramic-Hybrid bearings combine corrosion-proof, cryogenically treated nitrogen steel races with Silicon Nitride Grade 3 ceramic balls in a proprietary process that results in the ultimate high performance bearing setup. The deep-groove design raceways allow for maximum sized Grade 3 Silicon Nitride ceramic balls for for increased contact area and improved performance and longevity. 90% fill Kluber NBU52 grease only runs better and smoother with time and is highly resistant to being washed out. It is engineered to stick to the balls and continually be pulled back into the ball path where it is needed.The 12 tooth upper pulley/14 tooth lower pulley set 5mm bolt-holes is designed as an upgrade for SRAM 12 speed cable-actuated Eagle derailleurs (includes XD-15 cable idler pulley.)Enduro Derailleur Pulleys are available in a number of configurations and performance levels, starting with Ceramic-Hybrid, Black-Oxide treated Zero Ceramic as a step up, and XD-15 Ceramic-Hybrid at the top of the line. All are proudly precision manufactured in the USA.Enduro Item Code: BKCJ-0501

BKCJ-0457 - 11/13 tooth, XD15 Ceramic Hybrid Bearing, Machined Delrin Derailleur Pulleys for 11 and 12 speed Shimano GRX Derailleurs (12 speed 2x derailleurs RD RX-820 & RD RX-825) (5mm bolt hole) The ultimate upgrade pulley. Guaranteed to last forever against corrosionPrecision machined Delrin Derailleur pulleys featuring XD15 Ceramic-Hybrid radial bearings for enhanced shifting performance and longevity. The updated Directline design features larger caps that help to minimize bearing movement and contamination.Like all of our Directline pulleys, these pulleys feature CN (tight clearance) bearings in the upper pulley to maximize shifting accuracy and C4 (loose clearance) bearings in the lower pulley to allow for chain-line movement.500 AF Delrin pulley material features a high mechanical tensile strength and rigidity, natural lubricity, high resistance to moisture, caustic chemicals, and UV, making these pulleys highly durable, rigid, and very smooth. Delrin also machines very cleanly and precisely. The inherent lubricative qualities of this Teflon-infused material greatly reduces friction when it interfaces with the bicycle chain. When compared to other pulley materials, 500 AF Delrin with Teflon offers significantly less drag than pulleys machined from aluminum or titanium.An Enduro Bearings exclusive, our XD15 Ceramic-Hybrid bearings combine corrosion-proof, cryogenically treated nitrogen steel races with Silicon Nitride Grade 5 ceramic balls in a proprietary process that results in the ultimate high-performance bearing setup. The deep-groove design raceways allow for maximum-sized Grade 5 Silicon Nitride ceramic balls for increased contact area and improved performance and longevity. 90% fill Kluber NBU 52 grease only runs better and smoother with time and is highly resistant to being washed out. It is engineered to stick to the balls and continually be pulled back into the ball path where it is needed.The eleven-tooth upper and thirteen-tooth lower size and profile with 5mm bolt-holes are designed as an upgrade for most 11 and 12 speed Shimano GRX 2X rear derailleurs, including: RD RX-810, RD RX-815, RD RX-820 and RD RX-825. (Use BKCJ-0361 for 12 speed GRX RD RX-822 SG and SGS 1X derailleurs)Enduro Derailleur Pulleys are available in several configurations and bearing performance levels, starting with Ceramic-Hybrid, Black-Oxide treated Zero Ceramic as a step up, and XD15 Ceramic-Hybrid at the top of the line. All are proudly precision manufactured in the USA.

BKCJ-0361 - 11 tooth, XD-15 Ceramic Hybrid Bearing, Machined Delrin Derailleur Pulleys for 12 speed Shimano XTR and XT Derailleurs (5mm bolt hole)The ultimate upgrade pulley. Guaranteed to last forever against corrosionPrecision machined Delrin¬Æ Derailleur pulleys featuring XD-15 Ceramic-Hybrid, radial bearings for enhanced shifting performance and longevity. Designed and manufactured for performance, these pulleys feature CN (tight clearance) bearings in the upper pulley to maximize shifting accuracy and C4 (loose clearance) bearings in the lower pulley to allow for chain-line movement.500 AF Delrin¬Æ pulley material features a high mechanical tensile strength and rigidity, natural lubricity, high resistance to moisture, caustic chemicals and UV makes these pulleys highly durable, rigid and very smooth. Delrin also machines very cleanly and precisely. The in therent lubricative qualities of this Teflon¬Æ infused material greatly reduces friction when it interfaces with the bicycle chain. When compared to other pulley materials, 500 AF Delrin¬Æ with Teflon¬Æ, offers significantly less drag than pulleys machined from aluminum or titanium.An Enduro Bearings exclusive, our XD-15 Ceramic-Hybrid bearings combine corrosion-proof, cryogenically treated nitrogen steel races with Silicon Nitride Grade 3 ceramic balls in a proprietary process that results in the ultimate high performance bearing setup. The deep-groove design raceways allow for maximum sized Grade 3 Silicon Nitride ceramic balls for for increased contact area and improved performance and longevity. 90% fill Kluber NBU52 grease only runs better and smoother with time and is highly resistant to being washed out. It is engineered to stick to the balls and continually be pulled back into the ball path where it is needed.The eleven tooth upper and 12 tooth lower size and profile with 5mm bolt-holes are designed as an upgrade for most 12 speed Shimano XTR and XT Derailleurs (5mm bolt hole)Enduro Derailleur Pulleys are available in a number of configurations and performance levels, starting with Ceramic-Hybrid, Black-Oxide treated Zero Ceramic as a step up, and XD-15 Ceramic-Hybrid at the top of the line. All are proudly precision manufactured in the USA.Enduro Item Code: BKCJ-0361

BKCJ-0341 - 11 tooth, XD-15 Ceramic Hybrid Bearing, Machined Delrin Derailleur Pulleys for 11 speed Shimano Dura Ace (9000 Series) and Ultegra (8000 Series) Derailleurs (5mm bolt hole)The ultimate upgrade pulley. Guaranteed to last forever against corrosionPrecision machined Delrin¬Æ Derailleur pulleys featuring XD-15 Ceramic-Hybrid, radial bearings for enhanced shifting performance and longevity. Designed and manufactured for performance, these pulleys feature CN (tight clearance) bearings in the upper pulley to maximize shifting accuracy and C4 (loose clearance) bearings in the lower pulley to allow for chain-line movement.500 AF Delrin¬Æ pulley material features a high mechanical tensile strength and rigidity, natural lubricity, high resistance to moisture, caustic chemicals and UV makes these pulleys highly durable, rigid and very smooth. Delrin also machines very cleanly and precisely. The in therent lubricative qualities of this Teflon¬Æ infused material greatly reduces friction when it interfaces with the bicycle chain. When compared to other pulley materials, 500 AF Delrin¬Æ with Teflon¬Æ, offers significantly less drag than pulleys machined from aluminum or titanium.An Enduro Bearings exclusive, our XD-15 Ceramic-Hybrid bearings combine corrosion-proof, cryogenically treated nitrogen steel races with Silicon Nitride Grade 3 ceramic balls in a proprietary process that results in the ultimate high performance bearing setup. The deep-groove design raceways allow for maximum sized Grade 3 Silicon Nitride ceramic balls for for increased contact area and improved performance and longevity. 90% fill Kluber NBU52 grease only runs better and smoother with time and is highly resistant to being washed out. It is engineered to stick to the balls and continually be pulled back into the ball path where it is needed.The eleven tooth size and profile with 5mm bolt-holes are designed as an upgrade for most 11 speed Shimano Dura Ace and Ultegra derailleurs.Enduro Derailleur Pulleys are available in a number of configurations and performance levels, starting with Ceramic-Hybrid, Black-Oxide treated Zero Ceramic as a step up, and XD-15 Ceramic-Hybrid at the top of the line. All are proudly precision manufactured in the USA.Enduro Item Code: BKCJ-0341

BKCJ-0340 - 11 tooth, XD-15 Ceramic Hybrid Bearing, Machined Delrin Derailleur Pulleys for 11 speed Shimano Dura Ace (9000 Series) and Ultegra (8000 Series) Derailleurs (5mm bolt hole)The ultimate upgrade pulley. Guaranteed to last forever against corrosionPrecision machined Delrin¬Æ Derailleur pulleys featuring XD-15 Ceramic-Hybrid, radial bearings for enhanced shifting performance and longevity. Designed and manufactured for performance, these pulleys feature CN (tight clearance) bearings in the upper pulley to maximize shifting accuracy and C4 (loose clearance) bearings in the lower pulley to allow for chain-line movement.500 AF Delrin¬Æ pulley material features a high mechanical tensile strength and rigidity, natural lubricity, high resistance to moisture, caustic chemicals and UV makes these pulleys highly durable, rigid and very smooth. Delrin also machines very cleanly and precisely. The in therent lubricative qualities of this Teflon¬Æ infused material greatly reduces friction when it interfaces with the bicycle chain. When compared to other pulley materials, 500 AF Delrin¬Æ with Teflon¬Æ, offers significantly less drag than pulleys machined from aluminum or titanium.An Enduro Bearings exclusive, our XD-15 Ceramic-Hybrid bearings combine corrosion-proof, cryogenically treated nitrogen steel races with Silicon Nitride Grade 3 ceramic balls in a proprietary process that results in the ultimate high performance bearing setup. The deep-groove design raceways allow for maximum sized Grade 3 Silicon Nitride ceramic balls for for increased contact area and improved performance and longevity. 90% fill Kluber NBU52 grease only runs better and smoother with time and is highly resistant to being washed out. It is engineered to stick to the balls and continually be pulled back into the ball path where it is needed.The eleven tooth size and profile with 5mm bolt-holes are designed as an upgrade for most 11 speed Shimano Dura Ace and Ultegra derailleurs.Enduro Derailleur Pulleys are available in a number of configurations and performance levels, starting with Ceramic-Hybrid, Black-Oxide treated Zero Ceramic as a step up, and XD-15 Ceramic-Hybrid at the top of the line. All are proudly precision manufactured in the USA.Enduro Item Code: BKCJ-0340

BKCJ-0311 - 11 tooth, XD-15 Hybrid Bearing, Machined Delrin Derailleur Pulleys for 11 speed SRAM Derailleurs (4mm bolt upper/5mm bolt lower)The ultimate upgrade pulley. Guaranteed to last forever against corrosionPrecision machined Delrin¬Æ Derailleur pulleys featuring XD-15 Ceramic-Hybrid, radial bearings for enhanced shifting performance and longevity. Designed and manufactured for performance, these pulleys feature CN (tight clearance) bearings in the upper pulley to maximize shifting accuracy and C4 (loose clearance) bearings in the lower pulley to allow for chain-line movement.500 AF Delrin¬Æ pulley material features a high mechanical tensile strength and rigidity, natural lubricity, high resistance to moisture, caustic chemicals and UV makes these pulleys highly durable, rigid and very smooth. Delrin also machines very cleanly and precisely. The in therent lubricative qualities of this Teflon¬Æ infused material greatly reduces friction when it interfaces with the bicycle chain. When compared to other pulley materials, 500 AF Delrin¬Æ with Teflon¬Æ, offers significantly less drag than pulleys machined from aluminum or titanium.An Enduro Bearings exclusive, our XD-15 Ceramic-Hybrid bearings combine corrosion-proof, cryogenically treated nitrogen steel races with Silicon Nitride Grade 3 ceramic balls in a proprietary process that results in the ultimate high performance bearing setup. The deep-groove design raceways allow for maximum sized Grade 3 Silicon Nitride ceramic balls for for increased contact area and improved performance and longevity. 90% fill Kluber NBU52 grease only runs better and smoother with time and is highly resistant to being washed out. It is engineered to stick to the balls and continually be pulled back into the ball path where it is needed.The eleven tooth size and profile with 4mm bolt-hole upper pulley and 5mm bolt-hole lower pulley are designed as an upgrade for most 11 speed SRAM derailleurs.Enduro Derailleur Pulleys are available in a number of configurations and performance levels, starting with Ceramic-Hybrid, Black-Oxide treated Zero Ceramic as a step up, and XD-15 Ceramic-Hybrid at the top of the line. All are proudly precision manufactured in the USA.Enduro Item Code: BKCJ-0311

BKCJ-0310 - 11 tooth, XD-15 Hybrid Bearing, Machined Delrin Derailleur Pulleys for 11 speed SRAM Derailleurs (4mm bolt upper/5mm bolt lower)The ultimate upgrade pulley. Guaranteed to last forever against corrosionPrecision machined White Delrin¬Æ Derailleur pulleys featuring XD-15 Ceramic-Hybrid, radial bearings for enhanced shifting performance and longevity. Designed and manufactured for performance, these pulleys feature CN (tight clearance) bearings in the upper pulley to maximize shifting accuracy and C4 (loose clearance) bearings in the lower pulley to allow for chain-line movement.500 AF Delrin¬Æ pulley material features a high mechanical tensile strength and rigidity, natural lubricity, high resistance to moisture, caustic chemicals and UV makes these pulleys highly durable, rigid and very smooth. Delrin also machines very cleanly and precisely. The in therent lubricative qualities of this Teflon¬Æ infused material greatly reduces friction when it interfaces with the bicycle chain. When compared to other pulley materials, 500 AF Delrin¬Æ with Teflon¬Æ, offers significantly less drag than pulleys machined from aluminum or titanium.An Enduro Bearings exclusive, our XD-15 Ceramic-Hybrid bearings combine corrosion-proof, cryogenically treated nitrogen steel races with Silicon Nitride Grade 3 ceramic balls in a proprietary process that results in the ultimate high performance bearing setup. The deep-groove design raceways allow for maximum sized Grade 3 Silicon Nitride ceramic balls for for increased contact area and improved performance and longevity. 90% fill Kluber NBU52 grease only runs better and smoother with time and is highly resistant to being washed out. It is engineered to stick to the balls and continually be pulled back into the ball path where it is needed.The eleven tooth size and profile with 4mm bolt-hole upper pulley and 5mm bolt-hole lower pulley are designed as an upgrade for most 11 speed SRAM derailleurs.Enduro Derailleur Pulleys are available in a number of configurations and performance levels, starting with Ceramic-Hybrid, Black-Oxide treated Zero Ceramic as a step up, and XD-15 Ceramic-Hybrid at the top of the line. All are proudly precision manufactured in the USA.Enduro Item Code: BKCJ-0310

BKCJ-0301 - 11 tooth, XD-15 Ceramic Hybrid Bearing, Machined Delrin Derailleur Pulleys for 11 speed Shimano Derailleurs (5mm bolt hole)The ultimate upgrade pulley. Guaranteed to last forever against corrosionPrecision machined Delrin¬Æ Derailleur pulleys featuring XD-15 Ceramic-Hybrid, radial bearings for enhanced shifting performance and longevity. Designed and manufactured for performance, these pulleys feature CN (tight clearance) bearings in the upper pulley to maximize shifting accuracy and C4 (loose clearance) bearings in the lower pulley to allow for chain-line movement.500 AF Delrin¬Æ pulley material features a high mechanical tensile strength and rigidity, natural lubricity, high resistance to moisture, caustic chemicals and UV makes these pulleys highly durable, rigid and very smooth. Delrin also machines very cleanly and precisely. The in therent lubricative qualities of this Teflon¬Æ infused material greatly reduces friction when it interfaces with the bicycle chain. When compared to other pulley materials, 500 AF Delrin¬Æ with Teflon¬Æ, offers significantly less drag than pulleys machined from aluminum or titanium.An Enduro Bearings exclusive, our XD-15 Ceramic-Hybrid bearings combine corrosion-proof, cryogenically treated nitrogen steel races with Silicon Nitride Grade 3 ceramic balls in a proprietary process that results in the ultimate high performance bearing setup. The deep-groove design raceways allow for maximum sized Grade 3 Silicon Nitride ceramic balls for for increased contact area and improved performance and longevity. 90% fill Kluber NBU52 grease only runs better and smoother with time and is highly resistant to being washed out. It is engineered to stick to the balls and continually be pulled back into the ball path where it is needed.The eleven tooth size and profile with 5mm bolt-holes are designed as an upgrade for most 11 speed Shimano derailleurs.Enduro Derailleur Pulleys are available in a number of configurations and performance levels, starting with Ceramic-Hybrid, Black-Oxide treated Zero Ceramic as a step up, and XD-15 Ceramic-Hybrid at the top of the line. All are proudly precision manufactured in the USA.Enduro Item Code: BKCJ-0301

BKCJ-0300 - 11 tooth, XD-15 Ceramic Hybrid Bearing, Machined Delrin Derailleur Pulleys for 11 speed Shimano Derailleurs (5mm bolt hole)The ultimate upgrade pulley. Guaranteed to last forever against corrosionPrecision machined White Delrin¬Æ Derailleur pulleys featuring XD-15 Ceramic-Hybrid, radial bearings for enhanced shifting performance and longevity. Designed and manufactured for performance, these pulleys feature CN (tight clearance) bearings in the upper pulley to maximize shifting accuracy and C4 (loose clearance) bearings in the lower pulley to allow for chain-line movement.500 AF Delrin¬Æ pulley material features a high mechanical tensile strength and rigidity, natural lubricity, high resistance to moisture, caustic chemicals and UV makes these pulleys highly durable, rigid and very smooth. Delrin also machines very cleanly and precisely. The in therent lubricative qualities of this Teflon¬Æ infused material greatly reduces friction when it interfaces with the bicycle chain. When compared to other pulley materials, 500 AF Delrin¬Æ with Teflon¬Æ, offers significantly less drag than pulleys machined from aluminum or titanium.An Enduro Bearings exclusive, our XD-15 Ceramic-Hybrid bearings combine corrosion-proof, cryogenically treated nitrogen steel races with Silicon Nitride Grade 3 ceramic balls in a proprietary process that results in the ultimate high performance bearing setup. The deep-groove design raceways allow for maximum sized Grade 3 Silicon Nitride ceramic balls for for increased contact area and improved performance and longevity. 90% fill Kluber NBU52 grease only runs better and smoother with time and is highly resistant to being washed out. It is engineered to stick to the balls and continually be pulled back into the ball path where it is needed.The eleven tooth size and profile with 5mm bolt-holes are designed as an upgrade for most 11 speed Shimano derailleurs.Enduro Derailleur Pulleys are available in a number of configurations and performance levels, starting with Ceramic-Hybrid, Black-Oxide treated Zero Ceramic as a step up, and XD-15 Ceramic-Hybrid at the top of the line. All are proudly precision manufactured in the USA.Enduro Item Code: BKCJ-0300

BKCJ-0195 - 11 tooth, Zero Ceramic Hybrid Bearing, Machined Delrin Derailleur Pulleys for 11 speed Shimano Derailleurs (5mm bolt hole)Precision machined Black Delrin¬Æ Derailleur pulleys featuring Zero, Black-Oxide treated, Ceramic-Hybrid Radial Bearings for enhanced shifting performance and longevity. Designed and manufactured for performance, these pulleys feature CN (tight clearance) bearings in the upper pulley to maximize shifting accuracy and C4 (loose clearance) bearings in the lower pulley to allow for chain-line movement.500 AF Delrin¬Æ pulley material features a high mechanical tensile strength and rigidity, natural lubricity, high resistance to moisture, caustic chemicals and UV makes these pulleys highly durable, rigid and very smooth. Delrin also machines very cleanly and precisely. The in therent lubricative qualities of this Teflon¬Æ infused material greatly reduces friction when it interfaces with the bicycle chain. When compared to other pulley materials, 500 AF Delrin¬Æ with Teflon¬Æ, offers significantly less drag than pulleys machined from aluminum or titanium.Enduro Zero Ceramic-Hybrid Bearings featuring Black-Oxide treated 52100 High-Carbon Chromium alloy races paired with grade 5 Silicon-Nitride Ceramic Balls with 90% fill, high-pressure, water-proof grease. Si3N4 ceramic balls reduce bearing wear and increase bearing life by eliminating steel on steel contact within the bearing. Black Oxide/Magnetite treatment to the races provides an extra level of corrosion resistance and extended worry-free performance.The eleven tooth size and profile with 5mm bolt-holes are designed as an upgrade for most 11 speed Shimano derailleurs.Enduro Derailleur Pulleys are available in a number of configurations and performance levels, starting with Ceramic-Hybrid, Black-Oxide treated Zero Ceramic as a step up, and XD-15 Ceramic-Hybrid at the top of the line. All are proudly precision manufactured in the USA.Enduro Item Code: BKCJ-0195

BKCJ-0190 - 11 tooth, Zero Ceramic Hybrid Bearing, Machined Delrin Derailleur Pulleys for 11 speed SRAM Derailleurs (4mm bolt upper/5mm bolt lower)Precision machined Black Delrin¬Æ Derailleur pulleys featuring Zero, Black-Oxide treated, Ceramic-Hybrid Radial Bearings for enhanced shifting performance and longevity. Designed and manufactured for performance, these pulleys feature CN (tight clearance) bearings in the upper pulley to maximize shifting accuracy and C4 (loose clearance) bearings in the lower pulley to allow for chain-line movement.500 AF Delrin¬Æ pulley material features a high mechanical tensile strength and rigidity, natural lubricity, high resistance to moisture, caustic chemicals and UV makes these pulleys highly durable, rigid and very smooth. Delrin also machines very cleanly and precisely. The in therent lubricative qualities of this Teflon¬Æ infused material greatly reduces friction when it interfaces with the bicycle chain. When compared to other pulley materials, 500 AF Delrin¬Æ with Teflon¬Æ, offers significantly less drag than pulleys machined from aluminum or titanium.Enduro Zero Ceramic-Hybrid Bearings featuring Black-Oxide treated 52100 High-Carbon Chromium alloy races paired with grade 5 Silicon-Nitride Ceramic Balls with 90% fill, high-pressure, water-proof grease. Si3N4 ceramic balls reduce bearing wear and increase bearing life by eliminating steel on steel contact within the bearing. Black Oxide/Magnetite treatment to the races provides an extra level of corrosion resistance and extended worry-free performance.The eleven tooth size and profile with 4mm bolt-hole upper pulley and 5mm bolt-hole lower pulley are designed as an upgrade for most 11 speed SRAM derailleurs.Enduro Derailleur Pulleys are available in a number of configurations and performance levels, starting with Ceramic-Hybrid, Black-Oxide treated Zero Ceramic as a step up, and XD-15 Ceramic-Hybrid at the top of the line. All are proudly precision manufactured in the USA.Enduro Item Code: BKCJ-0190