... whistle,Pressure Gauge,Back plate and cylinder. For field operation respiration. Has thermostablly, flame retardant, insulation, corrosion protection ... liters), breathing resistance small(‹700Pa), breathe comfortbley and free(through the converted switch, breathe the outside air ... used the polycabonate material, it has strong anti-touch scrape performance, automatic fog removing . The air valve is small ...