Battenfeld Brass Catcher has a steel frame that easily attaches to the picatinny rail of any AR with a mil-spec anodized-aluminum clamp. Clamp and wire frame are fully adjustable and work with most optics. Brass enter the bag without interrupting cycling or disrupting the bolt function of the rifle. Works with up to a one inch riser. Heat-resistant nylon mesh with zippered bottom for easy brass removal. Bag holds up to 100 rounds of empty brass.