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 Ceramic bearing save Your energy during riding 12T&14T, Approx weight: 7g+8g, save 80% than your original pulley Increases the gear-shifting efficiency by reducing the weight pressure applied to the rear derailleur Fit with Shimano Road bike Derailleur Dura Ace R9100, R9150, ULTEGRA R8000,R8050, 105 R7000, R7050 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