1A310035 CALGAZ Calibration Gas Mixture Equivalent by GASCO 50 PPM Carbon Monoxide, 50% LEL Methane, 25 PPM Hydrogen Sulfide, 12% Oxygen, Balance Nitrogen contained in a 10 Liter Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder connection Built in Aerosol Trigger, Calibration Certificate NIST, Made in the USA