The RRWAD, our heavy Duty Caster Kit is built to hold up to pressure! Beefy 3 1/2" Casters with integral locking brakes doubled with a thick premium grade plywood base provide all the mobility you'll need for any Road Ready AMP Rack System.The RRWAD raises the height of your rack system by 5". Mobility made easy. http://www.roadreadycases.com/pdf/RRWAD.pdf