The Northern Industrial machinery skate is designed to move heavy equipment and machinery. Load Capacity (lbs.): 4,400, Base L x W (in.): 10 5/8 x 4 1/2 x 4 3/8, Roller Size (in.): 3 1/4 x 4 Includes a hook so multiple units can be attached in a series 10 5/8in. x 4 1/2in. x 4 3/8in. 3 1/4in. x 4in. poly wheels Sold as a single