This lising is for 2 Pulleys Made of super strong Delrin Plastic, rotate with no noise Won't hurt your chain Narrow Wide design Oversize Pulleys and Hybrid Ceramic bearing save Your enegry during riding 14T, Approx weight: 8g/each, save 80% than your original pulley Increases the gear-shifting efficiency by reducing the weight pressure applied to the rear derailleur Make sure ur derailleur cage is long enough to fit the 14T pulley, ask me if U are not sure Fit with most Sram Medium& Long Cage MTB Rear Derailleur in the market: SRAM Eagle/XX1/X01/X01DH/X1/GX(1X11)-X-SYNC 11sp, Fit with most Shimano Long Cage MTB Rear Derailleur in the market: M985,M980,M9000,M8000..., but won't fit Shimano Medium Cage normally won't fit Short Cage Derailleur Information about Hybrid Ceramic bearing: Bearing Races Material: Chrome Steel 52100 Ball Material: Nitrided Silicon Ceramic SI3N4 Enclosure: Two Seals Enclosure Material: Rubber Seal