When I went to buy my 21sf, I knew the ambi mag release had been a problem for others here on GT. So I looked for the CA version of the 21sf that did not have the ambi mag release. But I couldn't find one, so I just got one because they were hard to find anyway and this one had a cool serial number, too: Mxx 001. Well, just this past week I was cleaning my 21sf and a part fell out of the inside of the gun. It was a part related to the ambi mag release. And now NO mags will stay inside the gun. So I called Glock tech service dept and spoke with John. He said they could fix it and send it back... but they were having quite a few problems with the ambi mag release and were not even making them that way anymore. Option 2 was what I wanted with one exception. They can turn my gun into an sf model with a standard mag release. Here's the catch: they can't just alter the frame for the fix. They have to replace the frame... and only the frame. So now I will have a different serial number on my new sf frame and my old serial numbers (Mxx 001) on my slide and barrel. It pi**es me off, but I would much rather have a functional gun with solid lock up on the mag release than keep running into this problem over and over. I guess I could have argued with Glock more... because this will hurt resale value for sure. But I don't plan on selling this so I guess its not a real big deal to me.... But my recommendation when shopping for a new Glock is: DO NOT BUY! any gun with the ambi mag release.