Made of steel for lasting durability and strength. Moves up to 10 chairs at once allowing fast, easy break down of rooms. Two swivel and two fixed hard rubber casters allow safe and easy maneuvering of chair stacks. For use with Model B449418, B449419, B449420 & B449421 only. Size is 22-3/4" L x 23-1/2" W x 3-1/2" H. Color finish is Black.