The ceramicspeed oversized pulley wheel system has been proven to be the fastest pulley system in the world, providing energy savings starting from 2.4 watts over standard Shimano systems. The ospw system for Shimano 9100/8000 is an industry leading product, chosen by many of the world’s leading cycling teams and professional triathlete’s. Featuring a 13-tooth upper pulley wheel and a 19-tooth lower pulley wheel to provide absolute optimisation of the rear derailleur. The upper and lower oversized aluminium pulley wheels come Fitted with either standard or coated ceramicspeed bearings.