The CST/Berger 57-AL500H is an Electronic Self-Leveling Rotary Laser. The AL-500H is fully electronic self-leveling (±5°) and provides accuracy of up to 1/8-Inch at 100-ft (3.2mm at 30m) with a working range of 1,000-ft (305m) when used with the LD-90 Rotary Laser Detector. Simple one button operation makes this 600RPM rotary laser easy to set-up and use. The durable design of the AL-500H features a heavy-duty protective cage for the laser beacon and co-molded water resistant rubber housing (IP54). The AL-500H is powered by 6 “AA” Alkaline batteries.