This device uses your existing scope or red-dot sight, along with the patented Speed Tape System, to provide unparalleled accuracy. Crafted of CNC-machined aluminum, this 7 oz. system is capable of helping you shoot 2" groups at 60 yards. You just sight in at 20 yards and 60 yards, select a provided Speed Tape customized to your bolt velocity and trajectory, and you&';ll be able to dial in shots from 20 to 80 yards consistently. Fits most popular crossbows that shoot at speeds from 260 to 410 fps. Easy two bolt installation.