HyFin Vent Chest Seal Compact – Twin Pack Headwear The Combat Shirt Is Perfect Shell 69 Wool 29 The Combat Shirt Is Perfect For Military And Tactical Personnel In The Field To Wear Under Hot Keep Your Contents Secure With The Dual Snap Button Flap Closure This innovative design provides 3 vented channels designed to prevent airflow into the chest cavity during inhalation while allowing air to escape through the vent channels during exhalation Advanced adhesive technology provides superior adhesion as the HyFin® Vent Chest Seal Compact Twin Pack is specifically designed to overcome adverse conditions in austere environments where the casualty may be covered in blood