The MAC Eye Brows' Brow Definer is ultra-skinny pencil, which makes it ultra-easy to use, i.e., drawing the perfect arch, defining individual hairs, and adding the right amount of color. I've tried powders, liquids, and so forth, with no success - always too much color-density, or too harsh lines.
This MAC brow pencil is for us, who are neither professionals, nor are those incredibly talented YouTube Teenies :)
Only brow stuff i've ever used, wish i could feel comfortable enough for anastasia... but this does the trick of filling in my brows without making it look overdone.
