4″ Rubber Wheel Double Ball Race Swivel 2mm Steel Frame 248 lb per Wheel Load Capacity This 4″ diameter Swivel Castor with Blue Wheel from Adam Hall is a heavy-duty rubber wheel in a steel frame. It features a double ball race swivel and supports up to 248 lb, and is best used in a set of four to create a steerable rolling platform that supports almost 1000 lb. The rubber wheel construction helps absorb vibration as it rolls.