Pocket Mask O2, Headstrap in Hard Case , Reusable Mask, Class 2An emergency requiring CPR can occur anytime, anyplace, to anyone. It's good to know the Laerdal Pocket MaskTM can always be there when you need it. Small enough to fit in your pocket, it can be carried with you at all times. The Pocket MaskTM product combines a low resistance one way valve with a disposable 3MTM FiltreteTM hydrophobic filter to help prevent the passage of liquids and secretions. Valve and filter act as barriers separating rescuer and