Strike Billet Ultimate Dust Cover features a quick detach mechanism that allows you to install or remove the dust cover in under 10 Seconds. It also includes an adjustable detent set screw in order to compensate wear on the receiver and increase or decrease opening power. Our patent pending noise-reduction padding also makes it nearly 100% silent during activation. Heavy duty machined billet aluminum construction. *We strongly recommended applying blue Loctite threadlocker to the ball-detent thread after being adjusted. Not Compatible with Aero Precision M4E1 upper receivers and Lantac E-BCG due to carrier and bolt design.Includes dust cover and 4 rubber pads.