I got a 22mm XL cartomizer glass tank from IBTanked, they have a 19mm (diameter) tank as well that sits flush on the ProVari. and If you have a ProVari ring, the 22mm sits flush on that at that point the whole device is flush. I use a low to standard resistance cartomizer. It worked best for me. I recently started learning on RBA's and atm im experimenting with sub ohm, but for my ProVari the next tank I would like to have is a kayfun or russian. (RBA's) which will save you ga son your trip to the local vape shop or save your money from shipping. ONce you have kanthal wire (100 ft for under 10 bucks) and 100% cotton balls (under 10 bucks as well) - both will last you for a lifetime, basically. at that point you'll only be spending money on q-liquid and not spending so much on clearos or cartos overtime. Kayfuns and russains are easy rebuildables.