yeah the fixxer simply takes the place of the freehub body, so off comes the ratchet and on goes a simple fixed aluminum cog holder... it does bolt into the hub body with a 10mm allen. i had some issue with it on an older xtr hub, where splines or "star" of the hub didnt match up quite right with the matching cutout of the fixxer, so the fixer rotated a little even fully cranked down which made me fearfull that a good skid would destroy a fine hub. the fixxer will not work with the old freewheel cassetts like "drews adaptor" is made for.