The VX-3i BDC model comes with a pre-calibrated dial for 5.56/.223 55gr rounds that let's you accurately adjust the dot out to 400+ yards. The Twilight Max Light Management System lets you see details others cant in those crucial low-light situations at the beginning and the end of the day. With a magnification range great for any situation, youre guaranteed to have the right tool for the job. The CDS-ZL adjustment allows for 14.5 MOA of bullet drop, which equals 500 to 700 yards of travel for most rifles. A push-button Zero Lock system eliminates accidental dial movement.