Recently purchased a MM2108TB. Several have said to buy the expensive Amplock U-BRP2516 but this seems similar to the Gorilla Coupler lock that I first tried for 2 5/16". It wouldn't even go on. Then I bought a Trimax Universal Lock {$50+} that went on but the way the bolt fit on top of the trailer ball looked like it could be easily pried off. I'm curious as to what have purchased or would advise.

