1 5/16" O.D. Aluminum tubing construction reinforced with solid welded joints. Strapping attachment moves vertically on bar to adjust for load size. 5" x 23" shoe is standard Replaceable steel skids protect frame and padded rails protect finished surface of load. Replaceable steel axle is protected by sturdy housing, and rolls smoothly on maintenance-free sealed bearings Flexible-belt stair climbers allow movement up and down stairs without damage to stairs or cargo Rolls on premium pneumatic tires.