IN-EAR DIGITAL METRONOME Metronome for groups. Pack of 2 units. The GM-1 is an ultra-compact metronome that fits in one ear in the same way as headphones. Multiple GM-1 devices can be used so that all group members can practice at the same tempo in sync. This makes it possible to use the GM-1 for group practice with marching bands or dance teams, and for rehearsals where you need to move. The canal-type earpiece fits comfortably and securely in your ear, allowing you to hear the metronome sound clearly amidst ambient sound. Weight: 9g. Included items: User manual, CR2032 lithium battery (3V), headphones (S, M and L).