I am using a 901@ 5v. At least I think I'm at 5v (2x 3v.,the cap is screwed down) Really AWESOME!! Totally satisfied!! 2-3 vapes, clouds of vapor almost effortless draw!!:w00t::w00t::hubba::hubba:
I am going to try 3.7 volts later. I don't know if I even care to try the 6,7volts as I am...