This is my 2nd purchase of this item, though the 1st was not from this seller or through Amazon.
The case is OK, but the mounting plate is all plastic and is not terribly durable. My 1st plate lasted me about 10,000 miles of light duty use.
I bought a replacement plate, then the lock on the case failed shortly after. I decide to replace rather than repair.

The post that the case latches onto is the weakest point. Might want to buy a spare mounting plate if you buy this case as they are not always available. You could also carry a couple of extra bungies just in case. Or, if you don't require quick removal of the case from time to time, you could just drill a hole in bottom of the case and bolt it to the rack. Wish they made a 40+ liter version with a metal rack at a similar price!
If you can swing it, or need a more durable unit, you may be better off finding a different case with a metal mounting plate.