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Convert your standard mil spec AR 15, M4, M16 lower assembly to use 9mm and .40 S&W Glock Magazines!  The Mag-AD series adapters install in seconds.  Boasting a last round hold open feature making them a breakthrough product and a must-have for law enforcement and civilian gun enthusiasts alike.

The Stern Mag-AD9 series adapters are made of aircraft grade aluminum, lightweight with ergonomic design.   

Note: These adapters require the use of a 9mm or 40S&W barrel, "depending on chosen caliber" and a Glock cut bolt.


Looking for a complete conversion kit?  We have you covered.
Click Here.

Already have a Colt Style bolt and want to use our system?  We have you covered.
Click Here

Don't Have a bolt, want one?  We have you covered.
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Don't Have a barrel, want one?  We have you covered.
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Technical Information:

⦁    Made in the U.S.A.

⦁    Constructed from 6061 T6 aircraft grade aluminum.

⦁    4140 NiB coated feed ramp.

⦁    Hard coat anodized type 3.

⦁    Sturdy Construction.

⦁    Ergonomic mag release.

⦁    Works with any mil spec ar15 lower receiver.

⦁     All gun components besides the Bolt and Barrel remain stock

Please visit the following link before purchasing to ensure compatibility with your setup.






53 Reviews Hide Reviews Show Reviews

  • 5
    Outstanding Product

    Posted by Doug Starkweather on Apr 8th 2024

    I now have 3 of these adapters and have not had a single malfunction. Works perfect in my AR9 and AR45 pistols.

  • 5
    Mag AD 9

    Posted by George Ebersold on Jun 26th 2023

    Shipping was fast.
    Very easy to install and worked perfectly on a select fire lower. Runs fast and reliable!
    Recommend to anyone looking to covert an ar15 lower to a reliable 9mm carbine!

  • 5

    Posted by Darrin Brawley on Jan 3rd 2023

    Went together perfectly and functions flawlessly.

  • 5
    Stern defense 9mm glock adapter

    Posted by michael harrington on Aug 12th 2022

    I was very impressed with this product. After trying various different 9mm receivers that would not run enhanced fire groups I saw a video of this one running on youtube. I decided to try this one. It works perfectly with all trigger that were tried . I have yet to have a malfunction as to date ! This is a little pricey, but worth every dime. I love the ability to switch from 9mm to 5.56 with the same lower. Just buy it , you will not be disappointed. Also I would suggest buying a PSA lower for this adaptor . It is a perfect marriage. Locks back every time !

  • 5

    Posted by Deondrai Ramsey on Aug 9th 2022

    This is an amazing product, so amazing that I now own two of them. I looked into the competitors similar product, I even have friends that own the competitors product, there is no comparison. Yes, you somewhat get the same end result from both products, but it's worth the few extra dollars to buy from Stern Defense. Last round hold open, better placement of the mag release, solid lockup, what else is there to say. I have experienced ZERO issues running this adapter in my setup, and I'm currently at 1,000 + rounds through my PCC. I'm a farmer in the high desert region of MT. It's quite dusty, and we experience extreme temperature changes. My PCC is my go to for when I'm running around on the quad doing farm stuff, and I run Stern Defense on that PCC. Don't want to spend the extra money? Be prepared to be disappointed. Thank you, Stern Defense!

  • 5

    Posted by H Allen Davis on Feb 24th 2022

    I've built several dozen AR platform rifles and pistols over the last decade, many of them as PCCs. I've now built two 9mm AR-15 pistols using the MAG-AD9 adapter, and for my money, it's the absolute best way to go, no doubt. The Stern Defense adapter is far superior to all its competitors, too. The thing is not just well-built, it's rugged in the extreme. Using this adapter in a standard AR-15 lower gives you the flexibility to keep your AR-15 instantly ready for use as a conventional caliber weapon, be it a 5.56mm, .300 BLK., or any other chambering. This is a huge consideration for folks who are limited in only being owning a single AR rifle or pistol. In addition, the last round hold-open is drop-dead reliable, too (and if yours doesn't work, blame the magazine). The MAG-AD9 is the best way to go no matter what, even if you intend to use your weapon as a dedicated 9mm rifle, carbine or pistol.

  • 5
    Mag ad9

    Posted by Eric on Jan 18th 2022

    Awesome build quality. Have ets 32rnd Glock mags which fit/ function perfectly. Zero complaints, would recommend

  • 5
    Awesome Product

    Posted by Sok Chun on Dec 6th 2021

    So far is the best conversion block than others, Thanks Stern!!

  • 5
    purchased with 9mm upper

    Posted by Col.451 on Nov 29th 2021

    Excellent quality and am headed to range this week with it. Pricey but you get what you pay for. Fit and finish superb and the shorty upper is exactly what I've waited for.