This kit features a built-in interlock system that only one wrench is needed to tighten the hitch ball to the mount. Reese Towpower 21791 Reese Towpower Class III Interlock Ball Mounts Reese Towpower Stainless Steel Class III Interlock Ball Mount is rated for 600 pounds tongue weight and 6,000 pound gross trailer weight. Class III has a 6,000 pound gross towing capacity Reese Towpower | 21794 | Interlock® Trailer Hitch Ball Mount, Fits 2 Inch Square Receiver, 5.25 Inch Drop, 4 Inch Rise, 5,000 lbs. Capacity, Black The 2 inch square hitch bar has a 2 inch drop to level your trailer and add to the safety and ease of towing. Reese Towpower Stainless Steel Class III Interlock Ball Mount is rated for 600 pounds tongue weight and 6,000 pound gross trailer weight. Aazon.co: Reese Towpower 21790 Stainless Steel Class III Interlock... Reese Towpower Stainless Steel Class III Interlock Ball Mount is rated for 600 pounds tongue weight and 6,000 pound gross trailer weight. The 2 inch square hitch bar has a 2 inch drop to level your trailer and add to the safety and ease of towing. This kit features a built-in interlock system that only one wrench is needed to tighten the hitch ball to the mount