These square metal Caster Inserts feature a hardened steel, double star design that inserts firmly into any Square Tubing or Square Leg and is not easily removed. The square double star caster inserts are specially designed to sit deep in the tube allowing equipped items to roll over thresholds, extension cords, cracks in the floors and more without fear of the connector slipping out. Our double star connectors work with any quality caster such as Outwater's extensive line of threaded wheel casters. These inserts are available in a variety of popular sizes and fit 16-18 gauge (approximately 1/16" to 1/8" walls). The edges of the connector fit flush to the outside edge of the tubing for a clean, finished appearance.