This heavy-duty trailer coupler lock offers excellent security for RVs, trailers, and boats, fitting 2-5/16 inches cast/bulldog coupler. Made of durable carbon steel, it resists tools like crowbars and drills. The powder-coated surface and 304 stainless steel lock cylinder avoid rust, while the lock is easy to install and comes with 3 keys for added convenience. | Vevor | | Trailer Coupler Lock, Fits 2-5/16-Inch Cast/Bulldog Trailer Couplers, Heavy Duty Trailer Hitch Lock with 3 | Black | Best Buy