1.Easy to mount brass catcher keeps empty cases off the ground and prevents hot brass from hitting anyone near you. 2.An incorporated hook and loop strap wraps around the forearm of any AR-15, keeping the catcher sely against the weapon.  3.A thick wire frame holds the catcher opening in the correct shape over the ejection port, preventing it from interfering with the rifle’s cycling.  4.Zippered bottom allows you to empty the bag without removing it from your rifle.  5.Easily holds 60 shell casings.