Have You Ever Wondered Why Some Glock Mags Have A Silver Rectangle?

If you have spent any time in a gun shop you know that hardly anyone knows exactly what that little silver rectangle on the front of the magazine is for. During a Glock armorer’s course I took recently I made a point to ask the instructor what in the hell the exposed metal was all about. Sadly he had no idea why the Glock 17 and 19 magazines have the exposed metal window but a quick phone call to the Glock mothership and he was able to answer my question.

Image courtesy of AR15.com user --bullseye--

Image courtesy of AR15.com user –bullseye–

It turns out that there was a limited amount of Glock 17MB and 19MB pistols produced with a factory ambi magazine release. Here in the states we only saw a very limited run of the Glock 21SF that had the new ambi magazine release, specifically a rarer picatinny rail model that was only offered for sale for a short time.


With my understanding of how the standard mag release works, I was a bit baffled as to how the ambi unit operates. Thankfully YouTube user Customchannel filmed a quick video of him modifying a troublesome mag release on his Glock 21SF.

While I like Glocks just as much as the next guy, I really dig that 21 SF of his. I think I might have to be on the hunt for one to use as a suppressor host as a result of how much of an oddity it is.

Patrick R

Patrick is a Senior Writer for The Firearm Blog and TFBTV Host. He likes guns and has liked shooting guns for as long as he can remember. You can follow Patrick on Instagram @tfbpatrick, Facebook, or contact him by email at TFBpatrick@gmail.com.

The above post is my opinion and does not reflect the views of any company or organization.


  • Nicholas C

    I knew this already. I think I learned about it on a Glock forum.

    • Patrick R. – Staff Writer

      Would you like a sticker?

      • Andy Hills

        I would! As i would like to support the TFB!!

      • Nicholas C

        LOL is it a gold star participation award sticker? YES!!!

        • Bill

          You want the “Thanks for showing up” medal also?

      • Drew Coleman

        How about a cookie instead?

        • Patrick R. – Staff Writer

          Have you seen me lately? I clearly ate all the cookies.

          • Drew Coleman

            YOU MONSTER!

  • Eric S

    You say ambi mag release but later say ambi safety.

    • Patrick R. – Staff Writer


      • LazyReader

        We’re not all prefect

        • Holdfast_II

          Eye new that!

  • DanGoodShot

    Where it makes contact with the mag it looks internally identical to my H&K VP9 mag release.

  • olivehead

    Maybe I’m just dense, but I’m not following what the little rectangle of exposed metal is for as to the G17 and G19, and what the G21SF has to do with any of it. Could someone explain for the slower folks in the room?

    • Jess Johnson

      Nope, not just you. He switched mid article from explaining the identification to something about a 21sf.

      • Patrick R. – Staff Writer

        All three share the same mag release system.

        • Jess Johnson

          So all three share the original single cut on one side.

          The midel metal window is for the ambi.

          Then there is a third style with dual cuts and the metal window.

          Clear as mud!

          • Patrick R. – Staff Writer

            You got it!

          • noob

            hmm why did the ambi release fall out of favor? it sounds like they could have debugged it a little and made it standard

          • Bronson

            It’s unnecessary since you can switch the mag release to either side.

          • Soren Franson

            Because there were numerous instances where the mag catch assembly would drop out of the weapon together with the magazine.

          • Patrick R. – Staff Writer

            Because the Gen4 was released.

      • Kafir1911

        Thank you, me too.

    • The G17MB, G19MB, and G21SF all had ambidextrous magazine releases. The ambi magazine release engaged the cut in the front of the magazine body. However, the G21SF is the only one of these three that was distributed on the US marker.

    • Kafir1911

      Thank you.

  • TheNotoriousIUD

    I have this exact model.
    Give me a gold star.

    • Cal S.

      *Gold star*

    • Vhyrus

      I am pretty sure you could get an actual gold star from a collector looking for a rare glock like this.

      • TheNotoriousIUD

        Is it actually that rare? I havent heard this until today.

        • Patrick R. – Staff Writer

          Not that rare, no. They weren’t available for very long. Values seem in line with standard G21 pistols.

          • TheNotoriousIUD

            Yeah, I didnt figure.
            But I did think it was odd never seeing any with rails like mine.

          • Harry’s Holsters

            Military Arms Channel did a video on his years ago and I remember something about them being recalled because of the magazine release. I think he said because of that a lot were sent back and traded for regular G21s.

          • Patrick R. – Staff Writer

            That is correct. I never saw that particular video.

  • mrsatyre

    Wow! I’m an absolute n00b at guns when compared to 99.99999% of the people here, and I actually have known this since Gen 4 came out. My hat size just increased.

  • Interesting, I actually have wondered about that cut in the magazine. Cool article, Thanks!

  • Gary Kirk

    Not, really.. Kinda figured it was something to do with a mag release different than the ones I have dealt with

  • Harry’s Holsters

    Didn’t know that! I just thought they were trying to show there was metal throughout the whole magazine. Awesome gun for sure. There is something very special about a glock that their isn’t millions of.

  • GhostofBrowningNagle

    had one of these used at my local glock-specialty gun store. price was really low. i asked why and he said they aren’t that desirable…something about the mag release mechanism being prone to problems if i recall.

  • Andy

    I had one of these and remember making my own cuts on the front of regular G21 mags because these were in short supply. The ambi side mag release was located in the perfect spot to gouge my hand, so I filed it off. I also watched two different 21SF mag releases break during matches. At that time, there was no way to repair them and the gun was unusable. They were recalled for a reason. They aren’t “rare”. They are garbage. You mailed your frame back in and got a gen 3 frame back about 2 months later, with a different serial number than your slide/barrel. They obviously scrapped the idea on all other models.

  • 2ThinkN_Do2

    Nope, never wondered and still don’t; most likely never will, don’t own a Glock, no reason to.

    • maodeedee

      The reason that you don’t own one is because it’s more fun being a Glock hater and posting your meaningless comments on forums like these than it is to be someone who has actually owned one and knows what they’re talking about.

      I didn’t used to like Glocks because I thought they had mushy triggers. Then I shot a Glock 20 that a gunsmith had re-worked and it was like a different gun. Now I own one just like it and it’s on of my favorite handguns which is not to say that I can’t also enjoy my Hi-power’s, 1911’s, CZ’s, and Colt and Smith & Wesson revolvers.

      • 2ThinkN_Do2

        Nice try. I agree with the CZ’s and S&W revolvers though.

        • Kafir1911

          Went to the range yesterday, shot two CZs. A 75B, a 75BD Police and a Glock 17. Enjoyed all three. And I will admit I was surprised. I actually shot the 17 best. Even thought I thought the CZs felt better in my hand. Glock sights were better. All three were as from the factory.

  • Tactical Tightwad

    The ambi cut is on G26 magazines as well.

  • Mmmtacos

    Is this neat? No, this is depressing. Glock clearly can make a gun with an actual Picatinny rail and ambi mag release.


    “lol no fu”

  • Old Vet

    Was anyone else curious as to why he didn’t use an empty mag to prove how great it worked?? I am also just a little paranoid of people putting in loaded mags to show how great something works. Just one little “Oh sh*t moment” away from an accident.

  • HAHA73

    It’s HOT

  • Rocketman

    I have a question that no one around here seems to know. I own a used model 19 that has the serial number where you would expect it and after that it has the suffix “US”. I was guessing that this gun was originally from a U.S. government agency like the DEA. Can anyone confirm?

    • Patrick R. – Senior Writer

      Does it say “USA” on the slide? If so, that is a US made Glock. Plenty of them on the market.

  • Gunner4guy

    Just looked at all my spare mags for my GEN1 G19 and nearly 3/4(around 10 or 11) of them have the SF cut even though I got these in 2002. Possible Glock shipped them(or made them) ahead of the time they made/shipped the SF or Gen 3 guns??? Got to say I prefer that M1913 rail more than the Glock version on my G34. To me it just looks better.

  • Lightning

    Click bait and switch. Pretty poor writing. If the writer does know the answer to his bait question, he’s done a good job of hiding it.

    I often observe that the grade of people in the firearms community is decidedly better than outside it. This piece of BS is an embarrassment to the community.

  • Frank Grimes

    If you didn’t know this already, what are you doing writing for a gun blog?

  • Trevor_Phillips

    1911 like a Glock but for men.