Aqua Lung Impulse 3 Non Flex Snorkel Uses a two-valve system Patented Comfo-bite mouthpieces, which does not require the user to clench their teeth, eliminate jaw fatigue An optional, smaller size Comfo-bite is available Comfo-bite mouthpieces are replaceable The flex model allows the lower unit to drop away for use with a regulator Also available in a non-flex, standard version