2-in-1 Digital Angle Finder Meter Protractor Ruler Rule 360&deg; Measure 2x200mm Digital stainless steel angle rules make precise measurements for easy woodworking Lock and reverse angle features for all types of work Hinge mechanism allows a full 360-degrees to measure inside outside and reverse angles Large easy to read LCD display The battery life is around 200 hours and is protected by auto shut down after 6 minutes.