Elevate semi-trailers to loading docks for maximum serviceability during loading and unloading operations. Manufactured from heavy-duty aluminum tread plate for positive traction. All welded aluminum construction. 30,000 lbs. uniform capacity per pair (¼" thick material). Wheel Risers are designed to raise the trailer for loading and unloading to facilitate compliance with OSHA/ANSI B56.1 part 3 sec 7requirements for maximum grade of ascending or descending loaded fork trucks.