Wixey WR418 18-Inch Digital Protractor
The WR418 Digital Protractor has 18-inch long blades and offers +/- 0.1 degree accuracy and repeatability.  They include a “Miter Set” feature that instantly calculates the proper angle for cutting perfect miters. They have a range of +/-180 degrees and the heavy duty aluminum blades include embedded magnets in all edges to allow them to attach to cast iron tables and other steel surfaces for easy angle setting. The simple functions include an ON/OFF button and a ZERO button. After measuring a corner angle the 3rd “Miter Set” button calculates the exact miter angle for a precision fit.