So I recently made the mistake of buying a g-pen for vaping honey oil (I got the snoop dogg travel kit pictured here http://www.marijuanapackaging.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/s/n/snoog-dogg-g-pen-travel-kit.jpg) and after the first tank breaking in 3 weeks and replacement tanks being super pricy (30+ dollars in Canada) I started looking into alternatives. I found out g-pen batteries have 601 threading and that KISS Cartridges are really good cartridges and they have 601 threading so I don't need an adapter. What I don't understand is the difference between the 3.7V and 7.4V cartridges (http://www.planetvape.ca/kiss-cartridge-titanium-3.7-volt.html vs http://www.planetvape.ca/kiss-cartridge-titanium-7.4-volt.html). If anybody could help me decide which one of these will work best with my g-pen battery, or even recommend other replacement tanks, I would be super grateful