I have a Serpa I use sometimes but I have disabled the lock , I had set my pack down a couple times and one evening I tried to pull my M&P out and the lock was stuck I found some dirt had gotten in there and fouled it up. I did not want that to happen when I needed the pistol out in a pinch so I took the lock out, I added a little fleece stickum pad on the inside of the holster for more resistance.