Zipp 303 Firecrest Rear Wheel - 700 12 x 142mm Center-Lock XDR Tubeless Black A1. 303 Firecrest Tubeless wheels are designed for the real world… a world of imperfect conditions road surfaces and elements where the bottom line is simple. Efficiency = speed. Redesigned with a purpose-made approach for the demands of modern bikes; with reduced wind resistance rolling resistance rider fatigue and weight. The 303 is faster lighter and more capable over varied terrain—whether the surface is pavement in all its conditions or no pavement at all.