The waterproof formula is long-lasting and smudge-proof. The Precise Lash Building Brush allows you to get the result you want, allowing the lashes to go from everyday to dramatic in just a few strokes for clean separate finish without the clumps. Conditions as it thickens. Waterproof. Why you'll love it. Formula glides on smoothly to build great-looking lashes. Lash building formula makes lashes look fuller. No clumps. Ophthalmologically tested. Suitable for contact lens wearers.