If you have a current set of Zipp wheels, they'll come with the new 188 rear hub. It's the one with the preload collar on the left side. Of course, they are available to fit Shimano/SRAM or Campagnolo, but we don't think your initial choice of freehub body design should lock you into a component group for the life of your wheels. This is why we're offering loose Zipp 188 Freehub Bodies. This way, you're free to choose what components you run on your bike since the freehub bodies are so easy to replace.This body is specific to the 188 hub. If you have the previous Zipp rear hub iteration, the Zipp 182, you need a different body, which we also sell. The 188s have a larger axle diameter. The 188, so named for the weight, is held together with a 2mm pinch bolt that goes into the preload collar on the non-drive side of the hub. Loosen that, and you can pull the axle out from the right side. With the axle out, you can easily pull out the cassette body. Make sure to catch the .25mm washer that goes between the body and hub shell. Zipp makes both Campagnolo-splined and Shimano/SRAM-splined freehub bodies for the 188 hub shell. The .25 mm spacer goes between the body and hub shell in both Campy and Shimano-SRAM. If you are running Campagnolo 11-speed cassette, Zipp recommends putting a second .25mm spacer between the body and hub shell.