The Reese Towpower Black Nickel 2" Carbon Forged Interlock hitch balls have a patented hex design which allows for a one-wrench tightening system when used with a Reese Interlock ball mount. It makes for installing the hitch ball more efficient, and prevents marring of the hitch ball. It is not limited for use with the Interlock ball mount, and can be used with any standard ball mounts.