Universal Combo Lock Set with Hitch Lock and Coupler Lock (RHC33) by CT Johnson Enterprises®. 5/8" x 2-5/8" Hitch Lock Size. 1/4" x 2" Coupler Lock. What can be more fun and rewarding than boating on the open waters? This is an excellent solution for your boating needs. This product is great for use in all marine applications. It will satisfy the needs of both pleasure boat enthusiasts and ambitious yacht owners. Get this excellent product for your vessel and prepare to embark on a thrilling adventure.