CASTERS YOU CAN KEEP - Our Premium replacement caster wheel stem diameter is 7/16 inch(11mm),stem length is 7/8 inch(22mm), duty design supports up to 500 lbs as a set of 5 SMOOTH & QUIET ROLLING - Wheel materials are made of high-quality polyurethanes, which are high mechanical strength, wear resistance, shock absorption and low-noise. These features help roll easily and cause no squeaky sounds or noise of any kind. SAFE FOR FLOORS - Smoothly and quietly roll around on any hardwood, ceramic tile, wood, carpet, especially cement floors without scratching, please pay attention to due to less resistance force EASY TO INSTALL - Simply pull your old casters out, then plug the new wheels in, universally fit for standard seats: work stools, office chairs, dining chairs, desk wheels, tool carts etc colour:Black Material:PU size:50mm Package Contents: 5 x Caster Wheels Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.