Using KGD wick material, I have found that the wicks work great with a thick 7mm wick or a thinner 12 mm wick, or pretty much anything in between. I eyeball it because I have a good feel for the density. Since KGD splits off in layers, there's a wide variety in widths because of the variety in thicknesses of the wick. I'll bet they all pretty much have about the same material, though, as described. I have not had a leak since using the KGD now for six months at the slots. I come through the slots between 2.5 and 3 mm, again depending on thickness, and never so long as to be in the threads at the base of the tank. The longer the wick comes out of the slots and the wider/denser it is also ensure that I never get dry hits. With my wicks like this, I can vape my juice all the way until it no longer wicks at all, and then some before a dry hit. The dry hit is my reminder to fill the tank probably most of the time. I've used them all, wicking materials that is, and, for me, nothing surpasses the KGD, including Rayon and ceramic. Regular cotton does not approach KGD, imho. But, others have had good experiences with all these materials, so I know it's all about individual preferences and tastes. To each their own. Good luck!