I also received this small object, thanks to the black box of the musician!

Well it works well and is very precise, turn the dial to the desired note (E1, B2, G3, D4, A5 and E6) are oriented to 12 LEDs of the string corresponding box, if the projected light the rope stops to walk is granted, and next hop rope!
on the other hand I confess that my eyes are a bit broken from having tested this thing ...

Ergonomics standard after this tuner is the smallest I've ever seen, it is the size of a pick and it cost appears in the 15 Euros, we like it or not, we do not ruin!