Ultra-Fab Products Megahitch Lock Coupler Vault for 2 inch and 2-5/16" couplers The Coupler Vault from Ultra-Fab Products is the ultimate in trailer protection. The patented box style design completely encloses the trailer coupler when it is not hooked to your tow vehicle making it impossible for a thief to hook on to your trailer and drive away. The box is made of 3/16″ and 1/4″ hardened steel, and then powder coated to prevent rust. The stainless steel locking mechanism will not rust or corrode. The adjustable bolt ball allows you to adjust the height to fit tight into your trailer coupler. Once adjusted and locked into place the loose fit on your coupler does not allow anyone to try to attempt to cut on it with a hacksaw or saws-all.