14mmx8mmx4mm bearing fits over the driveshaft, take off the sproket slip it over the driveshaft until it touches the hull . ( yes you must also remove the fake outer gear cover) Get a 5mm thick piece of metal , aluminium , plastic , drill 14mm hole in it. You must also cut down the outer size so it fits inside fake gear cover. push down drive shaft over bearing. Fix this to hull side. now you need a thin piece of metal sheet alumin , plastic to same shape but only with an 8mm hole This goes onto the thick piece and holds bearing from escapeing, screw, glue in place. You will have no movement except turning of the sproket. This vastly helps with track throwing being greatly minimised.