To properly mount a phono cartridge, you need to be able to position it so that it remains tangent to the record grooves at all diameters. This is always a compromise. This gauge helps you to mount the cartridge to the headshell for the best compromise. The protractor lets an amateur do professional phono cartridge alignment. In just a few simple steps, the Protractor gives precise alignment for better sound and longer stylus life with any standard phono cartridge and radial tonearm. Made of durable 2mm ABS plastic allowing you to precisely adjust your cartridge/stylus by providing a clear top view. Easy to follow instructions included! Unlike similar market alternatives, our protractor is UV Printed and cured for 3 hours ensuring the highest quality print: so you'll never have to worry about paint peeling off like with comparable products! Guide: 1. Place this protractor on your turntable platter with hole over spindle. 2. Move cartridge/ tonearm until stylus rests exactly on center of bulls eye. (120.9mm radius). Check that cartridge is square with outer set of grid lines. - If not, loosen cartridge mounting screws and twist cartridge lightly until it is square. 3. Move cartridge/ tonearm until stylus rests exactly on center of inner bulls-eye (66.04mm radius), Rotate protractor around spindle as required. Check that cartridge is square with inner set of grid lines. - If not, change overhang, (move cartridge in or out along the axis) until cartridge is square. 4. Repeat step 2 and 3 till cartridge is square at both points. Tighten mounting, and recheck as above. Remove Protractor. Relax and enjoy!