This 4" x 2" flat tread thermoplastic rubber heavy duty kingpinless rigid caster with roller bearing provides smooth and quiet operation, and is safe to use on all floor types. Precision raceways and fully heat-treated construction make our 71 Series the ideal solutions for applications exposed to rugged conditions or high amounts of impact and shock. 71 Series are more durable than competitors case or induction-hardened construction, and longer lasting than conventional kingpin designs. These kingpinless casters eliminate kingpin failure, the leading cause of caster failure. Zinc plating provides an attractive, protective finish.