The famous M·A·C Stack Mascara is now Waterproof and smudge-proof for 24 hours! This must-have, buildable and clump-proof mascara provides an extra volume effect that defies gravity, lengthens and curls lashes in an instant, and ensures a flawless look thanks to the NEW waterproof formula. The Drench-Defense technology allows the product to wrap around each individual lash, repelling water and humidity.