There's a spacer that goes between the cartridge bearings in the AA TX-2 adapter. As shown, the first bearing is held in place by a snap ring. Also note the needle bearing in the second main bore of the adapter plate. The needle bearing is included with the TX-2 kit and also needs to be driven into the adapter plate. Since the needle bearing's housing is rather delicate, it should be installed carefully. Mike's experienced hands tapped everything into place sans drama or damage.