Osprey Global BDC Elevation Turrets For Tactical Riflescopes, .223 Remington, 165 Grain, Black, TA223BDC

These are very easy to use by zeroing your weapon at 100yds and compensating by simply winding the knob counterclockwise to your distance marked on the turret. The Tactical bullet drop compensators are backed by Ospreys lifetime warranty.