The reason the eye liner is called the "Master Duo" two in one liquid liner is the peculiar sponge tip applicator. It is tapered but at the tip there is a flat circular enlargement so by twisting the liner 90 degrees, you get either the thick side of the thin side.
However, this is pure gimmick, the enlargement at the tip is clumsy, it actually makes it harder to draw both thick and thin lines because you have to hold it in a very particular way to get the desired width. It's hard to articulate, but I assure you that if you have trouble with the normal tapered sponge tip, this will be a nightmare to work with!
To make matters worse, this liquid eyeliner has a crappy formula! It slightly burns the skin around the eyes. I personally can get over that because the sensation lasts only a few minutes. However, the problem with the formula is that it takes very long to dry and it dries very flaky (it shrinks a bit too).
Anyhow, the bottom line is no, if you have been eyeing this, don't buy it because it is total waste of money. Hope you found this helpful, I was pretty brutal with this one.