As far as I know there were Three main versions of the Powerbites, 1st gen had a solid axle & no pedal inserts, 2nd gen with 1pce pedal inserts & later a hollow axle, 3rd gen 2pce pedal inserts, hollow axle, drilled for rhd/lhd & at some point I think various small changes to the shape of the arms around the sprocket bolt area to allow smaller sprockets. Then there was the slimmer, lighter Hollowbites.