SH Terzzo is a 3-band equalizer with phase invert switch for acoustic and classical guitar. With the 3-band equalizer-controls (bass, mid, treble) you will be able to adjust your personal, acoustic sound easily. Phase switch inverts the signal and cancels the overall feedback. SH Terzzo comes with a passive Nanoflex pickup and an endpin connection. The 9V battery is under the preamp and is easily accessible. The LED will turn on when the battery power is low and battery should be replaced within 30 minutes. Fastening screws are fixed into the plastic plugs - and not into the wood of the instrument. Volume, bass, mid & treble control, Phase invert switch, incl. Nanoflex pickup incl. endpin output connector, Cutout dimensions: 70,5mm x 48mm (2.8'' x 1.9''), Outer bezel dimensions: 88mm x 57,5mm (3.5'' x 2.3'')