The Rubbermaid 4520-88 2 Shelf Utility Cart is made from structural foam molding. This material will not rust, dent, chip or peel and is idealf or heavy duty jobs. The material allows the cart to be lightweight and maneuverable and the non-marking casters allow the cart to be used on any surface. Maximum weight for this cart is 500 Lbs. The 4520-88 replaces the Rubbermaid 4520 cart.