You basically want to experiment with the size of the piece of blue foam to find what works best.
You have to make it a little wider than the cartridge, or it will probably leak and/or easily flood your atomizer.
On the other hand, if you cut it too wide, it will not wick as well when you stuff it in.
Usually you would want to cut it anywhere from 1/8 to 1/4 wider than the cartridge.
A lot of people will also recommend to cut it shorter and make a "plug" out of it, but that is a little more involved.
I'm sure there are
threads in the cart
mods subforum about it though, if you become interested.
