These motors have sleeve bearings at the top and bottom and the spindle rides on the bottom sleeve. If you gently move the pulley up and down you will feel a small amount of play between the two. Years ago people discovered that by making the motor ride between the two sleeve bearings (on a pad) improved sound quality by reducing motor noise. Solutions, however, using bits of plastic, springs and grease were haphazard to say the least. 

This motor thrust bearing is in effect a miniature main bearing, consisting of a phosphor bronze bearing shaft, housing a lubricated 4mm hardened steel ball. This assembly glues on to the base of the motor and the motor spindle rides on the ball, but does not touch the sides of the shaft. The height at which the ball sits in the shaft is adjustable by means of a grub screw, so once mounted you simply tighten the grub screw until the motor spindle is lifted off the bottom motor sleeve. The motor spindle now runs on a proper bearing - and is less noisy! 

This is an elegant, compact and lightweight solution. It comes complete with the allen wrench needed to adjust it. Any deck using this motor will benefit significantly - even those already fitted with some form of thrust bearing. The quieter the Turntable motor, the lower the noise floor. This is why so many purchasers comment on how much more information they hear after fitting this. You really need to have the deck upside down to fit it (or at least have the motor upside down) but it is very easy to glue it on. Incidentally, my experiments have shown that although the superglue holds it solidly in place, should you wish to remove it, it will snap off with no damage to the motor. It projects around 10mm beneath the motor, so Rega owners will need to drill a small hole in the cover plate. On a suspended sub-chassis turntable there is plenty of clearance.