Nikon AS/AE Series auto levels feature waterproof, nitrogen-filled, high-power telescopes that help you make precise measurements even in the wettest conditions. They feature a unique automatic air-dampened compensator to prevent magnetic interference, and an endless horizontal fine drive to ensure smooth, precise pointing and angular measurement. AS/AE Series auto levels are easy to set up and easy to use. All four models can attach to both flat- and spherical-head tripods, and the standard optical sight lens helps you find your target quickly, easily and accurately. A mirror with a pentaprism lets you view the circular bubble as an erect image during setup and sighting.