A primer is used as a base for eye shadows, it makes the shadow last longer and makes the colour look better too.
I dont really know wat is the best primer in those brands.
Primer is really good to make your eyeshadow last long and look smooth. It helps keep it in place and prevents creasing. I use it when I have to do some serious eye makeup for a party or formal occasion. The one I use is by MAC in Shimmersand. Love it.
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