COMPATIBLE COUPLER SIZES - Fits Select 50×50, 50×60 Couplers, and 2-5/16" A-Frame Couplers. Not Compatible With Adjustable, Bulldog, Lock Trailer, 50mm, Ring/Pintle, or 1-7/8" Couplers. The Rhino USA Trailer Hitch Coupler Lock Kit is engineered to withstand the harshest weather conditions. Whether it’s rain, snow, or intense sunlight, the anti-rust powder coating and heavy-duty chromoly steel core ensure your lock remains strong and functional, providing you with reliable security.