Zipp 303 S Rear Wheel - 700 12 x 142mm Center-Lock XDR Tubeless Black A1. 303 S Tubeless wheels provide today’s cyclists the versatility they demand with the speed they crave. A key innovation in the 303 S Series is the ideal-for-every-terrain rim design featuring a 45mm rim depth and a 27mm width designed to optimize tire profiles at lower tire pressures. That helps to reduce rolling resistance and provides a more compliant ride. The 303 S borrows design concepts from the higher-level 303 Firecrest Tubeless wheels to gain speed through increased efficiency achieved by creating a wheel with reduced wind resistance rolling resistance rider fatigue and weight.