These rear axle sliders fit over the nuts or into the large allen head hole on the axle so the outside diameter od the slider is supported against the axle block or fork leg to give the best rigidity. They are tied together with a 3/8 solid aluminium tie rid, one end is loctited and the other screws into a ss threaded insert for strength and longevity. Front sliders are bolted to the solid axle the axle needs to be drill and tapped M8 each end . We can do this for $20 inc freight back if you send it to us.