Feature: it is cnc machined by AL 7075-T6 round rod ,finished machined by diamond cutter,with diamond metal texture and good abrasion resistance index , it adopts imported Japanese steel bearing,rotating without resistance ,it greatly decreased frictional resistance,and increased cycling efficiency, the design inreased bike derailleur shifting speed ,it causes no noice when shifting speed k and prevent bike chain falling . Product Name: Jockey Wheel Bicycle Rear Derailleur Pulley Size:12T,14T Adapt to the bike speed: 7/8/9/10/11/12 speed Acrew axis:Fit for 4/5/6 MM roller screw axis Body: 7075 aluminum alloy Diameter:50mm(12T),55mm (14T) Bearing:ceramic bearing ,stainless steel shell , more durable Copper Bushing , Resistant Color: red black blue gold Green Net Weight: approx 14.9g Apply for most of rear derailleur on the market Package: Narrow-Wide teeth Rear Derailleur pully *1 pcs Copper Adapter * 2 pcs(4mm,5mm)