I bought this unit just over a year ago. I use it in addition to a Proven Locks 2516 AS towbar lock. I usually use the trailer 8-10 times a year. When I wanted to open the Trimax lock for a trip over the weekend, the key didn't go far enough into the lock to open it. I sprayed lube on the lock and let it sit for an hour but to no avail. I always use the protective cover that comes with the lock so nothing gets in the lock. I decided to cut the block off the tire so we could continue. It took less than 30 seconds with a cordless saw to cut out a sector of the cake that allowed me to bend my arm and remove it. I expected it to be a lot harder to remove. Save your money and invest in a quality towbar lock, not something that gives you a false sense of security.