I've looked around for these & was wondering if they're hard to get. Most of the sites I've checked list them as out of stock. I've read that these when used with HV give you an awesome vape since the LR's limit the voltage you can use them at. Anyone have any experiences with them on the ProVari and if they really do give you an improved vape? What voltages can these be brought up to on a ProVari? I know its subjective but just want to see if they're worth trying out.