GU-3 is an onboard EQ for Ukulele that has 2-band EQ, main volume control, built-in accurate chromatic tuner and LED display. Low Batt. Light will remind the user to replace the battery when the battery gets low. The compact size makes GU-3 easy to install into a Ukulele. The visible portion of GU-3 is only 39mm * 57mm * 37mm.