Caster Works Inc 5" Universal OEM or replacement shopping cart casters have double ball swivel raceways and zinc plated finish, polyurethane on polyolefin wheels with ball bearings and come with standard 1/2-13 x 7/8 threaded stem with key lock base. 5/16 Axle and nut. We recommend replacing in pairs... (ie: both fronts or both rears)