4 Buttons. One for voltage up, one for voltage down. Press both at the same time and it locks the voltage. A third for on/off plus it doubles for checking how much battery is left. Then the big one that fires it. Mine doesn't do this, but that version also checks ohms, I think you use the Fire button for that, but I'm not sure. They're a lot less complicated than a ProVari, although that's probably the one and only "advantage" they have. Oh, they're a lot lighter than a ProVari also, cause they're made out of aluminum. Mine has held up quite well, but I'm REALLY careful with it.
OK, continuing with my 20 questions, I see three buttons on Adam's picture (enlarged). Want to guess what those are? And I assume the FIRE button is on the other side near the top? Do you ever accidently push those three buttons when depressing the FIRE button? Also, is it just the way the picture is or is that a beveled profile at the bottom of the lavatube? 12 questions remaining on my allotment.
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