Wheelchairs, Mobility Scooters and Accessories MJM International R4TW Replacement 4″ Caster Set (Pack of 4) Review Posted on June 13, 2018November 7, 2018Author Marauderby Product Description Replacement 3″ rust proof threaded stem casters / set 2-lock 2 non lock. Manufacturer Contact Information 800-270-6199