Urban Six Tier Shelving Unit Sturdy shelves capable of withstanding an incredible 600-lbs per shelf with even distribution When used with the optional commercial quality casters, this shelving unit rolls easily across the floor, then securely locks in place (casters decrease shelving capacity to 400-lbs/shelf) Raised grids on the backside of each shelf; helps keep items from falling off backside Adjustable shelves allow you to change the configuration as your storage needs evolve Easy assembly lets you to construct in minutes a shelving unit that will last for years NSF certified Limited lifetime warranty