Reese professional 5/8" trailer coupler and receiver lock is the most theft-resistant lock in the towing industry. Its superior strength is derived from a patented locking design that does not require shaft diameter reductions which can cause weak points in other models. Ball-bearing lock system prevents theft, even if the lock is broken. The bearings extend and remain in the shaft, inhibiting lock removal. Durable chrome construction includes a rubber cap to keep tumblers free from dirt. Square key design virtually eliminates lock picking. Comes with two keys.