Features: 4 Angles Unit Switching: measures angle in (degrees), % (percent), mm/m IN/FT. Auto-reverse reading of LED display. V-Groove Built-in Magnets on the Base: V-Groove at the measurement base for easy attach to round pipes for accurate measuring. And the powerful magnet to secure the attachment to iron or metal surface. Groove on the 2 Sides of Housing: for easy doing the mark work. Auto-off Low Battery Indicate: after about 3 minutes of non-using the equipment, it will switch off automatically. Powered by 2pcs 1.5V AAA batteries, and has low battery indicator. Data Hold: hold-function to freeze the measurement, thus you can move the device to read the display. Audible Buzzer: audible tone with different beep frequency at -1.00~-0.05, 0.00, +0.05~+1.00; -89.00~-89.95, 90.00, +89.95~+89.00. Other Features: set zero function at any angle, self checking accuracy, self calibration, etc.