Laser focus gauges on keychain. Large ease to see numbers. Get your focus exactly right, no more guessing. Simply select what mm focus you would like for your project, set it on your material, and drop your laser head down to the desired focus. Size range included is from 4mm to 12mm with .5mm increments in between. (17 piece guage set) Comes with two wire keychain loops, (loops will vary in color). Use one of the two loops to put your most used gauges on, if you like. Easily store your keychains on your laser with a hook, hook not included.