The Korg Contact Microphone CM-200 is a contact microphone that can be attached to the bridge of your instrument, captures the sound of your instrument and sends it directly to your tuner.
The microphone uses a piezo element to capture vibrations and send them to your tuner through a 1.5m shielded cable. Indispensible in situations where the mic built into your tuner might have difficulty detecting the sound of your instrument (e.g.when practicing with an entire band).