For transportation industry, transportation operations in factory or in logistics warehouses Lightweight and durable Pro Tool Dolly Elastomer resin wheels reduce tire marks. The silent casters make it quiet. By exposing the ribbed structure to reduce weight, and the noise of the ground and wheel pass up, it is less likely to generate reverberation and more quiet. Dents on the side of the main unit to help prevent cargo from collapsing (rope for tie-downs sold separately). Handles can be stacked when folded. Finished product. Caster diameter: 3.9 inches (100 mm) Adjustable casters and fixed casters (2 each). Anti-slip rubber: 4 large pieces in the center of the top plate, 8 small on the screw for mounting casters Replacement casters: TYSFHG-100SL (free), TYSR-100SL (fixed) Compatible stopper: MPK-700FB