Master Lock Trailer Lock, Trailer Coupler Lock, Fits 2-5/16 in. Couplers, 378DAT LOCK APPLICATION: Best used for vehicles, trailers, and RV hitch locks EASE OF USE: Trailer hitch lock is easy to install and remove DURABLE DESIGN: Trailer coupler resists rust and corrosion; Advanced locking mechanism resists picking and prying SPECIFICATIONS: Fits 2-5/16 in. couplers INCLUDES: One coupler lock, two keys