Don't let your trailer get stolen. Coupler locks from CT Johnson are designed to prevent attaching to an unattended trailer. All coupler locks will lock your trailer to the hitch ball when in use. Fits most couplers requiring a 1/2? span (e.g. Shelby, Fulton, Dutton-Lainson). Features a patented pickproof screw-and-lock security with a 5-pin tumbler and 2-keys.