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.