CeramicSpeed OSPW X Pulley Wheel System Shimano GRX RX820 2x12 - Aluminum Pulley Carbon Cage BLKThis 13 tooth upper and 19 tooth lower OSPW System has been platform proven at races like Paris Robaix, Strada Bianche and CX World Cups The system is built for gravel and cross disciplines and meets the needs for durability, low friction and longevity The four spring tension settings allow customised setup based on ride conditions, and the handbuilt OSPW System offers custom molded carbon fiber cage for lightweight and durability Reduces friction 35