Up for auction is a set of two used swivel caster wheels. The overhaul height is 6 ½ inches. The wheels are aluminum. I used them on an engine stand and at that time the wheels were coated with some kind of plastic tread, which I removed. The part number for Colson is 4SER.5. The diameter of the wheel is 4 1/8. The platform holes are 4 1/2 X 4 1/8 center of hole to center of hole. There are two grease fitting on each one which can be seen in the picture. Can be used on one end of a shop bench for easy moving.