Made of high-strength annealed ductile iron, these Steel Machine Rollers have swivel tops that rotate 360 degrees on chrome steel ball bearings to allow for easier turning. The rollers form a "tank track" to revolve around a center load bearing plate in the frame to provide maximum maneuverability. The weight of the load is transferred directly from the load bearing plate to the rollers, eliminating axle friction and requiring less power to start and move. A spring loaded locking mechanism on the swivel tops, except on model VHMS-2, can be engaged in detents at 45 degrees intervals. These units are virtually maintenance free. Steering bars split in two and connect with sleeve for easy storage.