A couple of weeks ago I finally decided to contact Glock to see if they would replace my 21sf with ambi mag release. They said they would replace it and sent me a prepaid Fedex label to return it. They received my gun on Oct 18. I have not heard anything from them since then. All emails I sent were replied to within an hour. except the last one in which I asked when I might expect the replacement. That was one week ago and no reply yet.