This 13-tooth upper and 19-tooth lower OSPW system has been race-proven in competitions like Paris-Roubaix, Strade Bianche, and CX World Cups. The system is designed for gravel and cross disciplines and meets the demands for durability, low friction, and longevity. The four spring tension adjustments allow for custom setup based on riding conditions, and the hand-built OSPW system features a custom-molded carbon fiber cage for lightness and durability. CeramicSpeed OSPW systems reduce friction by 35-40% compared to standard pulley configurations. Compatible only with '2X-specific' GRX 810, GRX 815 derailleurs, as well as RX800 and RX805. If using a 1x drivetrain, a maximum 36T cassette can be used. In the package: Complete OSPW X System for Shimano GRX810/815 + RX800/805 CeramicSpeed UFO TECH Bearing Oil 15 ml dropper bottle for pulleys