GASCO 429-16 100 PPM Carbon Monoxide, 75 PPM Hydrogen Sulfide, 2.5 % Methane (50 % LEL), 16 % Oxygen, Balance Nitrogen Contained in a 650 Liter Factory refillable cylinder, For Use with Any and All Gas Detectors, Cylinder Connection: TBD Gas Specific, Calibration Certificate NIST, Made in the USA