Make sure your batteries are staying charged! This voltmeter reads from 08.0 - 18.0 volts. Connect 12 volts to the gauge and it will display voltage to the nearest 0.1 of a volt. Red, Blue, or Green LED display. Mounts in a standard 2-1/16" hole. Limited lifetime manufacturer's warranty. Made in the USA.  

NOTE: This gauge fits Peterbilt and Kenworth models; 2005 and older. Also fits Freightliner, International, Mack, Western Star, and Volvo models with 2-1/16" gauges on the dash.