Superior strength is built into every Reese Towpower Class V ball mount. Built tough for unparalleled strength, Reese heaviest duty ball mounts fight rust and corrosion with Metal Shield, a superior coating for years of protection from the elements. Reese Towpower Interlock design is a patented hex design which allows for a one-wrench tightening system when combined with a Reese Interlock hitch ball. It makes for installing the hitch ball more efficient, and prevents marring of the hitch ball.