Enduro rear derailleur jockeys are made from Delrin plastic, the highest grade bearings, and machined aluminum bearing covers, all made in the USA. The machined Delrin jockey will outlast any other on the market. Rear derailleur jockeys spin 3 times faster than your BB making the ceramic bearings all the more critical for making sure all your power drives you down the trail. The smooth action pulley also increases shifting performance and reduces overall drivetrain wear. This rear derailleur jockey sets work with SHIMANO 10 speed rear derailleurs and contain Grade 5 Ceramic sealed cartridge bearings with Chromium races, and low drag silicon seals. 9 grams