The Armasight CO-LR (Clip On Long Range) is a night vision unit that mounts in front of an existing day scope and converts the day scope to a night vision scope, effective up to ranges of 1000 yards. The CO-LR can be mounted to or removed from a standard Picatinny rail in seconds, with no tools required. The CO-LR is recommended for use with day scopes of up to 10x magnification. Because the CO-LR is mounted in front of your day scope, the shooters eye relief is not altered and shot release and follow through all remain intuitive. As the unit is factory bore-sighted to better than 1MOA accuracy, no alteration in zero is experienced, so it truly is as simple as mount-focus-shoot, as familiar as shooting in the daytime. Lens system is F1.54, F108mm.