The ShirtLock did an OK job of keeping my shirt in. My shirt pulled up and bunched a little bit, not as bad as if I didn't have anything, but way more than when I wear my shirt stays.

On the good side, like I said it did an Ok job, and it didn't set off the metal detector like the metal clasps on my shirt stays do. I have both now, so I'll stick with the stays for most days and use the ShirtLock when I need to travel or go to the courthouse.