The Zoom snorkel series has been developed, by Omer's technicians, specifically for Spear Fishing and Free Diving. The shape of the Silicone Mouthpiece and the Air Tube has been Ergonomically Designed to follow the Profile of the Spear Fisherman's Face, to greatly reduce its Visibility during the Dive. The Internal Diameter of the Tube is 0.8" (20 mm), a Specific Dimension to Optimize the Air Flow Rate. The Tube will undergo no Swelling in water and won't yellow under the action of UV Light.