Pallet Rack Add-On Units come with one pre-assembled upright and 4 beams (supports or wire deck sold separately. Our heavy duty pallet rack features 3" x 3" columns. Constructed from 14 gauge steel, our uprights offer a maximum capacity of 20,867 lbs. (based on a maximum shelf spacing of 48"). The new bolt together design provides a lower cost of ownership because components can be easily replaced when damaged during use, while traditional welded uprights require replacement of the entire upright.