Bulldog Hitch Coupler Lock for Locking Trailer to Truck Hitch. This lock has a hardened 7mm pin for wide lever couplers between 2″ and 2-1/2″. The 1/4 turn lock make installing and removing a breeze. The cap helps to keep dirt and debris out of the locking mechanism. This rugged lock can’t pop open or be false locked. Comes with 2 high quality tubular keys.