There are two different 11 speed cassette bodies for Mountain hubs. We've got them both. The XD cassette body fits Easton M1 and X4 hubs and accomodates XX1 and X01 cassettes. Fits on X4, M1-121, M1-221, M1-321 and M1-332 hubs. Must use one of the included driveside endcaps, the origianl endcap will not fit under the cassette without binding. Does not fit on M1-120 or M1-220. The Blue M1 cassette body fits Easton M1 and X4 hubs and has Shimano HG-E splines for eleven speed road cassettes. Use this to put a set of 29 mountain wheels on your disc brake cross bike with 11 speed drivetrain. Fits on M1-121, M1-221, and M1-321 hubs. Does not fit on M1-120 or M1-220, use the orange R4 body for these. Cassette Body