Heavy duty, high tensile extruded aluminum, Type 6063-T5 alloy. KSR SERIES: Frame constructed of 1 1/2" square heli-arc welded aluminum tubing. Shelves are 2-7/8 arch channels heli-arc welded to frame. Fully assembled and ready for use KAR SERIES: Each shelf corner has a heavy duty extruded aluminum collar permanently welded in place which accommodates the upright. A stainless steel set screw is provided in each collar to lock the shelf at the desired height. Shelves are 4" "E" Channel heli-arc welded. Tubular top shelf for general merchandise. Shipped knocked down, easy to assemble KAR SERIES: 4 "E" Channel Tubular Frame