GASCO 10L-453: Calibration Gas Carbon Monoxide 50 PPM, Pentane 50% LEL, Hydrogen Sulfide 25 PPM, Oxygen 12%, Balance Nitrogen contained in a 10 Liter Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder connection Built in Aerosal Trigger, Calibration Certificate NIST, Made in the USA