Dock & Boat Rolling Wheels These economy standard duty wheels measure 18" x 6 " diameter, have an 6" tread width,  450 lb. capacity and are roto-molded from polyethylene and U.V. stabilized. This premium material provides a tough, rigid wheel, and offers stress, crack and impact resistance, along with excellent performance in low temperatures, and prolonged exposure to petroleum products. Rolls easily over virtually any terrain and will not rust on the axle. Suitable for light wieght or Aluminum roll-in docks , they are easily mounted on a 1 1/2" OD axle. The axle opening is 1.98 inches. Commonly, a galvanized or 1.9 OD galvalume pipe is used, along with PVC pipe bushings on both sides of the wheel, and secured with cotter pins through the axle.