mine's only got a two position toggle. boost and normal i'm guessingIts an overdrive that matches best with el84 amps. Very bright - the more gain, the brighter it gets. The new ones have a 3 way toggle - fat / boost / normal. I run mine on boost mode, and it gives a bit of breakup and chime. Nice for semi-clean passages. It works great as a solo boost for a little added zing. Won't get heavier overdrive, just low to medium gain.