The Vari-Zone multiplex crossbow scope allows you to precisely compensate for the trajectory of any crossbow shooting between 240 and 360 FPS for up to 50 yards in EXACTLY ten yard increments. Simply sight for 20 yards on the crosshair, dial in your crossbows velocity, and you are automatically sighted for 30, 40, and 50 yards! This gives you the opportunity to change arrows without having to relearn the trajectory scale or else to perfectly tune your scope to any crossbow. The Vari-Zone is virtually parallax free at normal crossbow shooting ranges and has sensible adjustment clicks of 1/2″ at 20 yards.