I use it for some years. I have yet not had to change the 2 AAA batteries that I put the first new day! It is compact (10 x 6.5 x 1.5 cm) and features a built-in microphone for acoustic instruments. The small foot retractable rear (like picture frames) is sometimes convenient (the screen is not backlit).

1 input jack 6mm
A calibration 430-449 Hz
Tuning "quadra flat" (possibility to extend to 4 semitones, practice with capo)

Give any string instrument (violin, bass guitar, but I managed as bouzouki and mandolin), in standard or open.

One complaint: no output jack for use in series in its config.