I use nothing but VISION Stone II on my ProVari v.1, now v.2. Love the screw in end caps. Haven't lost a
tank Full pulling it out of my Bianchi flashlight holster since switching to the Stone
tanks. Some reason mine oHm out at 1.6 so I'm using 3.3v, sometimes less, on my ProVari v.2. JMHO
Cheers,
otrpu