Sylvan Arms AR-15 to 9mm Conversion Block for Glock Pattern Magazines – GCB100

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UTG GL933 33 Round Polymer Glock 9mm Magazine


Easily Convert Your AR-15 Lower to Accept Glock Magazines

The Sylvan Arms AR-15 to 9mm Glock Conversion Block – GCB100 is a drop-in addition that converts your AR-15 lower to a 9mm Lower for use with Glock magazines. This accessory is designed to install in Mil-Spec lowers almost exactly like a standard rifle magazine, without resorting to buying a separate lower receiver exclusively for Glock mags.

This fantastic conversion kit from Sylvan Arms is one of the best accessories on the market today and increases the modularity of your AR-15 pattern rifle.

Takes Your AR Build to the Next Level

The Sylvan Arms AR-15 to 9mm Glock Compatible Conversion Block is designed to fit into the magazine well of your standard AR-15 and reduces all the extra space and allows Glock 17 and 19 pattern magazines to fit. The fit and function of this adaptor are exceptional and genuinely ingenious which makes it one of the best AR-15 accessories on the market today.

It is machined from black oxide steel and 6061-T6 aluminum coated with a black anodized finish for extreme durability and wear resistance. This adapter promotes easy installation and swap-out when needed and takes your AR build a step further to switch that big 5.56mm-sized hole into a 9mm-sized one to fire your favorite 9mm ammo.


  • Easy to install and swap out
  • Accepts popular Glock 9mm magazines
  • Designed to work with Mil-Spec lowers
  • Does NOT include last round bolt hold open
  • Works with Glock® 17 and Glock® 19 mags
  • Built of 6061 aircraft-grade aluminum
  • Does not include last round bolt hold open


  • Material: Steel and 6061-T6 Aluminum
  • Finish: Black Anodized
  • Weight: 4.2 oz.

DISCLAIMER: This product is not manufactured, authorized, endorsed, or warranted by GLOCK. GLOCK does not warrant or represent that this product is compatible with GLOCK pistols.

Have Questions About this Product?

The AT3 Tactical store has a 90 day no-hassle return policy for products in good condition. You can view the full details of our return policy here.

If you encounter an issue or defect with a product after 90 days of your purchase, you can refer to the manufacturer for a warranty claim. Their policies are below.

Sylvan Arms Warranty

We stand by our products!

If you are experiencing an issue with a Sylvan Arms product, please contact us at your earliest convenience so we can address the issue. Our goal is to make it work for you so please give us all details possible. Not every product is 100% compatible, with variations in build, but we will do our best to make it work with your components.

We have a 30-day hassle-free return policy. If you would like to make a return please request an RMA number from our customer service department. We reserve the right to deny return requests if the item has been intentionally damaged beyond repair.

Contact Details:

  • Telephone: 888-256-5632
  • Email:

Disclaimer: Manufacturer’s warranty is subject to change without prior notice.

Customer Reviews

Based on 14 reviews
Excellent product

I bought this so I can run my 10.5" 9mm upper on my AR15 SBR lower. It ran with no issues. I does what it is designed to do. It is easy to install and remove. This is now one of my wife's favorite guns to shoot.

Thank you for your review. We're glad to hear that the conversion block worked well for you and that your wife enjoys shooting it too!

Scott Goad
Works great

Works great does what it's supposed to do.

Thanks for sharing your feedback! We're glad you're satisfied with your purchase.

Fred Hall
I bought two

I had convinced myself that last shot bolt hold open was absolutely necessary for my 9mm PCC AR project. Then swallowed twice and spent alot more money for a magazine adapter with LSBHO. Then spent too much time and effort trying to get it to accept differing brands of mags.

Bought the Sylvan Arms adapter and it accepts and functions flawlessly with any brand mag I throw at it. And who was I trying to kid thinking "tactical reloads" with LSBHO were necessary? Against paper targets, soda cans and a stray varmit or two?

Save your money for ammo and buy Sylvan Arms adapters. Theyre simple, solid and WORK.

Thanks for the review. I agree, the Sylvan Arms adapter is a great value and works flawlessly with any mag I've tried it with.

Jim Orfield
Great product

This thing works great, did have to lubricant and adjust a little. To be expected on anodized parts. Thanks

Thank you for your review. We're glad to hear that the conversion block works great and that you had no trouble adjusting it.

Earl Rocca
Sylvan arms conversion block

I have only ran 10 rounds through the gun. So far it operates better than I expected. The fit and everything about the conversion block is top notch. Will buy more in the future

Thanks for sharing your feedback! We're glad you're satisfied with your purchase.