There is no official approved list published by the ATF, but this minimalist, lightweight, brace seems to meet the guidelines. It has no padding in the back, and only a small contact area available for the shoulder. Plus, it is marketed as a pistol brace. I have one on our .22lr AR pistol for extra stability, and for protecting the buffer tube from damage. My.FDE one fits snugly, and looks great. It helps to put a little gun grease on the opening before installing it. Goes on smoothly, and slides easily.