The TWISTEP® Locking Bolt provides two benefits in one: • It provides an added degree of security and deterrent to theft. • It firmly attaches your TWISTEP® to your hitch receiver. The accessory includes: • A chrome plated steel bolt • The lock and 2 keys • Mounting instructions • It's easy to install. • Model #180 - 5/8" diameter for 2" receivers • Model #181 - 1/2" diameter for 1-1/4" receivers ADDITIONAL INFORMATION: Manufacturer: OT, LLC Type: Multi-Purpose Pet Step Locking Device Size: two sizes as listed above