5/16 X 22MM Precision Bearing. Ref # 608-RS. This is the most popular bearing in the wheelchair world. This bearing fits most caster wheels from 3″ to 8″. If your anti-tippers use bearings this is probably it. The Ref # can usually be found on the seal of the bearing Fits on most front caster wheels, including 8×2 wheels from Quickie Wheelchairs PRICE IS FOR A PACK OF 4 BEARINGS