The provides cost-effective protection against trailer theft. With a 1/2" hardened solid steel bar and pick-resistant lock, it's a great option for trailer protection. The universal design is compatible with all 1-7/8", 2", and 2-5/16" couplers. All BulletProof Locks are treated with an aircraft-grade lubricant for longevity. The locking mechanism is protected by a heavy-duty rubber cap. Comes with 2 keys. Compatible with all 1-7/8", 2", and 2-5/16" couplers Treated with aircraft-grade lubricant for longevity Locking mechanism is protected by a heavy-duty rubber cap | BulletProof Medium-Duty Coupler Lock