Super strong magnets hidden inside the bottom of the gauge securely attach the digital angle gauge to a magnetic surface. Specifications Range: +/- 180 degrees Resolution: 0.1 degrees Accuracy: +/- 0.2 degrees Repeatability : +/- 0.1 degrees Size: 2.3″ x 2.3″ x 1.1″ Battery: 1 – AAA Auto Shut Off: for extended battery life