This has been the biggest selling distortion pedal since its release in 1978.  I didn`t know why until I bought one and tried it the other day.  It has a very rich and musical sounding distortion. Not like heavy metal pedals which only have tons of gain but don`t sound musical at all.  I must say it`s a breath of fresh air in today`s world where the music is crap now. I find it to be a very versatile pedal as you can play many songs from Chuck Berry`s "Johnny B. Goode (distortion half-way) to 80s hard rock(distortion from half-way to all the way up depending on the song)  Musically, it has enough gain to cover almost anything you would want to play accept for something like crappy black metal or some other non-musical noise. Since I bought this distortion pedal I haven`t needed to buy another one because this has done everything that I have needed it to do. I recommend turning the tone knob all the way down or it will have too much treble.