Dollies have six abrasion-resistant, high-capacity cast iron steel wheels on fixed axles to move heavy machinery, containers, and other equipment. The center wheels project lower than end wheels for easier pivoting. Welded steel construction. Model 6,000 lb. models have a 3" channel steel frame; 5" x 2" cast iron wheels have roller bearings. 10,000 lb. models have a 6" channel steel frame; 8" x 3" cast iron wheels have roller bearings. Durable baked-in powder coat finish for added toughness.