Roadmaster 501 StowMaster Tow Bar Class IV. 6000 Pound Towing Capacity, 2 Inch Ball Mount; Adjustable Arms, Mount To Cross Bar. Stainless steel in virtually every moving component for smooth, trouble-free operation. Autowlok locking mechanism - allows both tow bar arms to extend or retract for a quick connection. Then, as you drive away, the arms self-center and automatically lock. Full-length safety crossbar - a full-length angle iron brace is integrated into the rear of the bar for maximum support. Self-lubricating nylon bushings eliminate friction between the inner and outer arms. Other tow bars use steel on steel. Plug-welded arms - steel plugs seal both ends of the tow bar, preventing corrosion from moisture and debris. A lustrous, high-tech powder coat finish for maximum durability.