12 Lock Size: This is a trailer hitch receiver and coupler lock kit, 5/8in diameter 3?1/2in long hitch receiver pin lock for type Class Iii Iv receiver, trailer coupler lock is 1/4in in diameter, 3/4in span. 2Antitheft Lock: Designed for long term hauling and safely protect your trailer, boat, camper, and more from theft, the trailer hitch can be installed quickly and easily for greater ease of use. 3Receiver Lock Operation: The trailer lock adopts a push to lock design, which can be easily pushed without a key. To open it, just turn the key slightly and the pin will bounce out on its own. 4Coupler Lock Operation: The coupler lock is easy to operate, with a screw type locking action that just turn the key 5?7 times to open or lock, saving you time and effort. 5Premium Materials: Made from high strength zinc alloy and coated with electrophoretic paint, trailer hitch lock is durable and rust resistant, and the dust cover is designed to keep the keyhole away from water and dirt.