I've pretty much tried all the wicking mediums and until recently used cotton in all my builds. I was a little leery due to the price but gave in and bought a couple of feet of ReadyXwick 3mm. After trying it I ordered more (slim). This stuff is by far the best wicking material that I have tried. It won't burn, is extremely absorbent and last forever. I can see a couple of feet of this lasting me a year. Although I haven't used it in a Protank I think the slim wick would be well suited for that application. The 3mm wick is fantastic. I wind a 28ga 3mm coil @ 1.25 Ω and the 3mm wick slides right in due to it not fraying when cut and it's a perfect fit. I've been running this set up all day for 2 weeks and the only thing getting dirty is the coil.