Draw-Tite Trailer Hitch Lock - 3 in. Square Receiver, 5/8 in. to 3/4 in. Pin Diameter, Professional Model 63260Draw Tite Trailer Hitch Towing Lock Model 63260 Trailer Hitch Lock, Fits 3 Inch Square Receiver, 5 8 Inch to 3 4 Inch Pin Diameter, Professional The Draw Tite 5 8 in diameter dogbone lock is primarily designed for towing and features a ball bearing pick proof design. Use it for securing class V towing ball mounts that have a 3 in sized receiver tube. For use with 3 In. square shanks Class V Bright zinc finish 4 In. span Pick proof square key Always