The primer it's self is white, as well. One coat will start to dry clear, but if you layer (which is a must), it stays white-ish. One coat doesn't seem to do much, but with 2 - 3 coats helps define my lashes, which seems weird because that means I'm putting more and more stuff on my lashes, but it's true. It also adds length, but no real volume. Sephora says:
I haven't noticed any fibers, and I didn't get a chance to use this under a Lancome mascara (I had other things to use up), but I tried this primer with They're Real! and Lashblast 24Hr, and it seemed to add soemthing to them. Neither mascara flaked without the primer, and there wasn't a difference in wear time or smudging, either.Give your lashes an XL boost. This innovative mascara base maximizes the result of any Lancôme mascara. Features micro-fibers for enhanced effect; triangular brush helps separate lashes.
To sum things up, this mascara added length for me, but little else. For $23, I would hope it'd do something really measurable, but I don't know if the cost is worth it. I probably wouldn't purchase this on it's own, but I'd happily use a sample.