The RRWED heavy duty Caster Kit is designed for Effect Rack cases. It features beefy 3 1/2 inch (8.9 cm) casters with integral locking brakes doubled with a thick premium grade plywood base for ease of mobility for any Road Ready Effect Rack System. The RRWED raises the height of your rack system by 5 1/4 inches (13.3 cm). See PDF brochure above for more details.