Two major problems with the reversible mag release...1) When you flip it around to accommodate a left thumb function, it now makes insertion of the mag a little difficult because of the way the tops of the mags are cut. There's a slightly slanted edge that allows the mag to glide past the catch until it's locked in. If you flip the catch, you now end up fighting the top of the mag, because it is not slanted to allow easy insertion on that side of the mag. I hope all of this makes sense. 2) The cut on the magazines to allow for a left handed mag release have a slightly different cut, which effects how the mag seats in the receiver. All of my casings were coming out bent...looked like the letter D. Flipped the release back around, problem corrected.