This is a replacement Tacx freehub body for direct drive trainers. The standard body of a Tacx direct drive trainer is not compatible with all cassettes. Use this body to suit your SRAM XD-R cassette. It's easy to place, and all you need is a 5mm hex key. The SRAM XD-R body is suitable for 11 - and- 12 speed SRAM XD-R cassettes. This version is for the Tacx Neo 2T.