Waterproof Formula. 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. Waterproof. For external use only. Keep out of reach of children. Always read instructions.