Description: The 12T 14T bike rear derailleur pulley can support 9, 10, 11 speed chains. With narrow wide design, it won't hurt the bike chain. It can save your effort during riding and it can increase the gear-shifting efficiency by reducing the weight pressure applied to the rear derailleur. Made of high-quality resin and ceramic bearing material, the derailleur pulley can rotate with no noise and is not easy to rust, solid and durable. The diameter of the 12T derailleur pulley is approx 4.8cm and the diameter of the 14T derailleur pulley is approx 5.5cm. It is suitable for SRAM XX1 Eagle/X01 X1/GX/NX/X9/XX/X01, for Shimano M8000/M9000/M980/M972/M780. Item Name: Derailleur Pulley Material:Ceramic,Resin Compatible Models: for SRAM XX1 Eagle/X01 X1/GX/NX/X9/XX/X01, for Shimano M8000/M9000/M980/M972/M780 Size Details: 12T Diameter: 4.8cm/1.89" (Approx.) 14T Diameter: 5.5cm/2.17" (Approx.) Notes: Normally won't fit short cage derailleur. Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement. Package Includes: 2 X Derailleur Pulleys(12T + 14T)