DEWALT's DW077 heavy-duty 18-v. self-leveling cordless rotary laser is accurate to 1/8-in. per 100 ft. and runs off DEWALT's standard battery system. For accuracy, an out-of-level shut-off mechanism automatically stops the laser if the unit is bumped out of plumb or level. A high-power laser diode produces an exceptionally bright and sharp mean. The beam is visible indoors up to 100 ft. from the laser and can be detected up to 1,000 ft from the unit with a digital detector.