This low level twin wheel castor has 40mm diameter rubber wheels, and a square top plate for easy attachment. These low profile rubber castors are small and discrete, and quiet on any floor surface. Ideal as furniture casters, or on equipment and point of sale display stands. You can also purchase the fitting screws, 4 per castor, to make attaching these low level castors a quick and easy job! TW 40mm Low Level Twin Rubber Wheel with Plate