Expanded metal boobox with the added strength of wall to wall frame conection. MODEL HEIGHT DESK C500 22''-29'' Adj 18'' x 24'' C503 22''-29'' Adj 20'' x 24'' C506 22''-29'' Adj 20'' x 24''OPTIONSPermaTuff EdgePlywood Core Work SurfaceSolid Plastic Work SurfaceNon-Skid GlidesQ-Ball GlidesBlack Edge