The SKB RLX4 4U Roll-X Case is made to carry audio equipment that fits into a 4U rack. The case has a depth of 17 1/2" and accommodates 19" rack mountable equipment. It is made of polyethylene rotationally molded plastic. It has a molded carrying handle, a retractable pull handle and 2.5" wheels. The Roll-X racks interlock and stack with each other.