BARSKA Tactical scopes are designed to give you as much control as possible for extreme type shooting. They have been designed with features like side adjustable parallax adjustments and a first focal plane Mil-Dot reticle that allows you to estimate range at all power settings. The Accu-Lock system utilizes a coil spring positioned within the scope to securely lock the inner tube. This coil positioning system allows the scope to stay locked on to the target shot after shot.