The Maxim Defense CQB Collapsing Arm Brace is

The Maxim Defense CQB Collapsing Arm Brace is one of the most comfortable braces on the market for how compact it is. This brace includes a set screw so you can set your length of pull where you want to. The buffer and spring are specifically made for this product. The buffer is standard weight and the spring shortened. There are two built in QD sling points on either side. You have four different length of pull options to choose from, making this a versatile arm brace for any AR15 pistol. 

* If you interested in vastly reducing gas blowback check out these custom heavy buffers

For more info, visit Maxim Defense