Premium UNIVERSAL 360 degrees of solid hardened steel" dual purpose coupler lock (fits Most couplers). UMAX100: Features an exclusive design that provides 360 degrees of hardened 5/8" - 16mm steel shackle protection for your unattended trailer. Provides instant security for your camper, boat or trailer when they are not hooked up to your vehicle. Also features 1/2 turn technology that cannot be false locked. Easy installation. Fits all couplers from 1 7/8" to 2 5/16". Ballistic grade nylon housing absorbs hammer blows, protects against weather. Huge 6 tooth, 3/8" wide locking lug system.