https://www.simplyscuba.com/products/mares-ergo-dry-snorkel The Ergo Dry by Mares is designed for maximum performance and a completely dry breathing environment. The mouthpiece is moulded in soft rubber for greater shock and water resistance and also there is an exhaust valve in the mouthpiece for prompt purging. The lower flex tube is made from corrugated silicone for effortless breathing and fits perfectly along the side of the face for superb comfort. Features Exhaust valve Corrugated hose and mouthpiece made with high quality silicone Super dry top Anatomical design