Model 3" rod 11*22 Material Polyurethane (PU) Swivel universal castor Specification3 inch Use furniture casters Diameter 75 (mm) Mounting height 103 Bearing double axle Wheel width 24 Range of application swivel chair, furniture Wheel thickness 24 (mm) This caster does not require a plastic office chair pad at all, the caster will glide safely over your vinyl material, almost any kind of carpet (except thick and high carpet), even expensive hardwood floors or tiles. Universal Rod Size - 7/16" x 7/8" (11mm x 22mm) fits 96% of standard office chairs sold on the market (please check your chair's wheel size before ordering to ensure it fits). The castors are made from top quality steel and high quality polyurethane and can hold up to 50kg on a single wheel, increasing to 250kg on 5 wheels. The vibration reducing polyurethane wheels will provide a smooth and quiet roll. Will not leave any marks or scratches. No tools required. Pull out the wheels of your old desk chair and push in the new castors until the foot bar is firmly seated and secure.