Elpex complete back wheel for Evolution V and X models measuring 70x40 mm. Standard speed 2 or slow speed 3. Speed 3 has longer wheel life so best to put 3 on the back and 2 on the front if doing a combination. Comes with anti reverse bearings, wheel spacers, axle, and nuts. Each wheel spacer is 5 mm thick and the hub is 34 mm wide. Axle length is 65 mm and slides up into 6 mm slot on the rollerskis.