The Caldwell Picatinny Rail Brass Catcher offers a convenient, consistent and easy to use method of collecting brass while shooting at the range. Unlike traditional brass catchers that attach using a non-adjustable, flimsy wire frame and one hook-&-loop fastener strap, this variant from Caldwell mounts securely to an AR-15 or AR-10 rifle equipped with a Picatinny rail system via an 2-piece aluminum clamp. This brass catcher's frame and clamp are fully adjustable to accompany rifles equipped with a variety of different optics. Several integral detent locks within the frame can accommodate rifle receivers of varying thicknesses. The catcher's nylon mesh bag is heat resistant and features a zipper on the bottom for easy removal of trapped brass. Bag can stow up to 100 empty .556/.223 casings.