Super-9 Track B1Clincher rim designed specifically for the velodrome Small hook tire bead designed for aero efficiency, and track specific carbon laminate Fastest with 23mm tires on the velodrome The wheel remains flat from its widest point to the hub and features a proprietary textured surface SRAM Model ID: WH SP9 TLTK B1 Attributes Axle Type Bolt on Hub Model ZR1 Track Rim Color Black Rim External Width 27. 5mm Rim Internal Width 21mm Rim Material Carbon Valve