In my humble opinion what the Lavatube needs next is an extension cap, similar to the Provari one, that will let you use a bigger variety of batteries. Just got some Ultrfire 2800mAh and sadly they do not fit, but they will fit my Don so they will not go to waste, but the limitation on 18650 batteries, as they vary in size, is a drawback that should be addressed by those who want it, so a simple extention ring or larger cap would be a real bonus.