Usage Tips: Professional guitar and bass tuner With volume, bass, middle, treble, pres control knobs. LCD display, easy to read. Low battery check LED. Auto and manual tuning mode. Powered by 6F22 9V battery (No Battery) Principle: Pick up the vibration of the bridge through the piezoelectric strip, drive it with 9V power supply, input it to the host computer, amplify the signal through the host circuit board, and output it to the speaker. This pickup is an active pickup. 1. Frequency Response: 20Hz~20KHz 2. Control Range: Bass: +/- 12dB at 60Hz Middle: +/- 12dB at 500Hz Middle 2: +/- 12dB at 1.2KHz Treble: +/- 12dB at 3KHz Presence: +/- 12dB at 8KHz Mid2. Control: 600Hz~2KHz 3. Tuning note: Chromatic/Guitar Mode 4. Chromatic & Guitar Tuning Mode(7B/6E/5A/4D/3G/2B/1E) 5. Pick-up: Piezo Ceramic Pick-up Colour:black Material:Plastic+Metal Size:9.8 x 5.5cm Package Contents: 1 x pickup 8 x screws 1 x wire clip 1 x pickup stick 1 x battery box 1 x strap Only the above package content, other products are not included. Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.