Small booster pedal which does exactly what is expected: boosts the signal without messing with the tone. There is also true-bypass feature which helps to keep the signal clean when not using the boost. Settings are super-primitive: just one knob which controls the amount of boost. Boost goes up to 20 dB which probably enough for most of the people, especially if you run the pedal on effects loop like me you get considerable boost on 9 o´clock settings.
This pedal can used on front of amp too, then amount of volume boost depends on the amount of headroom you have on your amp. On my high-gain amp you don´t really get much more volume but the boost overdrives your signal to get more gain. I don´t like this pedal as overdrive as much traditional Tube Screamer-type pedals (OD-1, Bad Monkey whatever), probably because I personally like to get bit of dirt from overdrive pedal, this pedal only pushes the input level on amp preamp-section.
For a simple boost pedal, this pedal works really good for me, I also like the size and how little it takes precious place on my pedalboard.