What Our Gearhead(R) Experts Are Saying: "This freehub kit is an essential upgrade for maintaining smooth drivetrain performance. Designed for the ZR1 hub, it offers seamless compatibility with SRAM XDR cassettes and ensures crisp shifting in all conditions."When every watt matters, a reliable freehub makes the difference between wasted energy and peak efficiency. The Zipp ZR1 XDR Freehub Kit is engineered for smooth, precise engagement, giving us the confidence to push harder on the flats and dig deep on the climbs. Built for seamless integration with SRAM XDR cassettes, this freehub helps maximize drivetrain efficiency while keeping our wheels rolling fast and smooth.