Kadaon Office Chair Wheels Casters Rubber PU Large 50mm Ideal for Hardwood Floors and Carpets Smoothness (Black & Sliver) - Best Quality Guarantee! Modern Design Resistant Polyurethane Material - No more scratches on Hardwood floor, or any type of floor. Standard stem size: 11mm (7/16") diameter, 22mm (7/8") length Maximum Weight Rating: 110 lbs. per wheel (Set of 5 supports 550 lbs.) Tested to ANSI/BIFMA Safety Standard 5 Years Manufacturer Warranty