Save yourself alot of money and get a Nikon Prostaff 2-7x 32mm shotgun scope for $129.00. It's all you need for a slug gun. The energy level of a 20 ga. slug is questionable beyond 150 yards for deer hunting anyway. Just zero in with the Prostaff at 100 yards, and your good to go for hunting from 0-150 yards as long as you center your crosshairs on the vitals.