This is an updated version of the Oversized Pulley Wheel System for Shimano 9100/9150 and 8000 SS/8050 SS. Mounting instructions for both this and the older version are to be found under our Support section. This new design has an integrated stop tower for easier mounting.The CeramicSpeed Oversized Pulley Wheels 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 9100/9150 and 8000 SS/8050 SS 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.Please note: The OSPW System for 9100/9150 and 8000 SS/8050 SS is NOT compatible with Ultegra 8000-GS (long cage) nor with the clutch equipped Ultegra RD RX800 & RX805. Please see our Shimano 11 Speed Pulley Wheels for a compatible upgrade.The Shimano 9100/8000 OSPW system is compatible up to a 32 tooth cassette for both Dura Ace & Ultegra derailluersIn The Box:A complete 13-tooth/19-tooth OSPW System,CeramicSpeed Bearing Oil in 15ml dropper bottle.