Features: 3-band equalizer, rotate the knobs (LOW/ MIDDLE/ HIGH) to adjust frequency. Wide frequency response range from 20Hz to 20kHz. With phase and tuner function. With feedback (NOTCH), middle frequency (250Hz-10kHz), and volume (VOL) control. Built-in high precision twelve-tone temperament tuner, with clear LED display for easy reading. Compact and lightweight, comes with 8 screws, easy to mount into the acoustic guitar. Powered by a 9V alkaline battery (not included). Low battery prompt: replace battery when "BATT" indicator lights up. Note: Size and color may be slightly different due to manual measurement and different light conditions. Thanks for understanding. Specifications: Color: Black Input Impedance: 10M Frequency Response: 20Hz-20kHz Power Supply: 1 * 9V Alkaline Battery (not included) Item Size: 80 * 56 * 27mm / 3.15 * 2.20 * 1.06in Package Size: 15.4 * 8.5 * 4.2cm / 6.1 * 3.3 * 1.6in Package Weight: 160g / 5.7oz Package List: 1 * 3-Band EQ Equalizer 1 * Battery Box 1 * Piezo Pickup Line 2 * Cut-out Template 8 * Mounting Screw 1 * User Manual (English)