SmartRack Caster Kit for SR4POST to be Mobile. Caster kit (4 pcs) for SR4POST Allows 4 post open frame racks to become mobile Includes casters installation guide and mounting hardware Heavy Duty 550 lb (per caster) rating A complete line of SmartRack accessories are available to customize your SmartRack to your application. Designed for easy installation and years of reliable service SmartRack accessories from Tripp Lite are ideal complements to your SmartRack enclosure or open frame rack system. Package Includes Includes casters installation guide and mounting hardware