Aluminum Gantry Crane Total Locking Caster set provides a number of benefits to an already worthwhile gantry crane. The durable construction generates a smooth roll with limited jostling. Simple to install with pre drilled mounting holes. Total locking caster set for holding a gantry crane in place. Works with steel gantry crane for maximum capacity. Glass-filled nylon in order to hold greater loads. Set includes four swivel casters for even maneuverability.