The Heininger Advantage Hitch Lock is the best defense for securing your trailer or bike rack to your hitch. Receiver lock for both 2 x 2 and 2-1/2 x 2-1/2 receivers. Use in place of standard pin and clip to prevent drawbar or accessory (bike rack/cargo carrier) theft. Fits 2 x 2 (Class III and Class IV) and 2-1/2 x 2-1/2 trailer hitches (Class V) or any hitch requiring a 3 span. Pin diameter: 5/8 Inside width: 3-1/16 Overall length: 6-3/8 .