If you think all of those fancy wand shapes and sizes are more about clever marketing than true function, you're about to get schooled.

According to Sarah Vickery, PhD, principal scientist for CoverGirl Cosmetics, formula isn't the only thing you need to consider when shopping for mascara. You can take the same mascara and apply it with different brushes and get totally different looks.

"Which formula you pair with which brush has a huge impact," says Vickery. In other words, the formula and the brush have to work together.

There are two types of mascara users: Those who do three swipes and call it good, and those who apply mascara like they're recreating the Mona Lisa.

If you're the "just a quick comb-through" type, use a wand that deposits a lot product so that those few swipes will completely coat your lashes. Vickery recommends a traditional wire brush (over the newer plastic ones), because it picks up a lot of mascara and delivers it to the base of the lash. You can use a plastic bristle, however. Just choose one with a wide core (the rod that the bristles poke out of). The fatter the core, the more product you get when you pull it out of the tube.

Because twisted wire wands aren't as good at keeping lashes clump-free, those who are more high-maintenance with their mascara application should go for a rubber brush &mdash: this will let you apply over and over again sans clumping.

According to Vickery, the CoverGirl Clump Crusher mascara was designed with these perfectionists in mind: "The precisely engineered tight spacing between bristles is smaller than the average clump size - so clumps are stopped before they even start forming on the brush."

A general rule of thumb when picking out a mascara wand: how the wand looks is how it's going to apply. A fat and fluffy brush will yield voluminous, fat and fluffy lashes. Getting larger-than-life volume and thickness is the most common look that women are after, says Vickery. So to pump up wimpy lashes, pick either a twisted wire brush or plastic bristle brush that is big and fat.

Try:
Marc Jacobs O!mega Lash, $26

Physician's Formula Organic Wear 100% Natural Origin Jumbo Lash Mascara, $9.99

Pixi Large Lash Mascara, $16

"For uniform, very defined separation and length, a comb may be your best tool," says Vickery. But you can also get length and definition with smaller brushes -- just look for ones that are plastic or rubber with closely spaced bristles. Ball shaped brushes also allow you to get extreme definition because the smaller shape allows you to get from root to tip, and to evenly coat each and every lash individually.

Try:
Make Up For Ever Smoky Stretch Mascara, $24

L'Oréal Voluminous Butterfly Mascara, $8.99

Givenchy Phenomen'Eyes Mascara, $30

For a winged lash look, choose a brush that mirrors the effect you're going for. "When people think about curl, curved brushes are what they think about," says Vickery. You can also try one that looks like an hourglass &mdash: the shape gives you the lift and curl of a curved brush while also getting to every last lash.

Try:
Benefit Roller Lash, $24

Dior Diorshow Iconic Overcurl Mascara, $28.50

Clinique High Impact Curling Mascara, $16