The Zipp 303 Firecrest Carbon Clincher Disc Brake Rear Rim sets the new standard for this new era in road riding. Road bikes are going where theyve never gone before, are expected to do more, and are being ridden harder than ever. With an all-new disc-specific, tubeless rim, the 303 Firecrest Carbon Clincher is now internally 21mm wide and faster than ever.