GASCO 429-16 100 PPM Carbon Monoxide, 75 PPM Hydrogen Sulfide, 2.5 % Methane (50 % LEL), 16 % Oxygen, Balance Nitrogen Contained in a 900 Liter Factory refillable cylinder, For Use with Any and All Gas Detectors, Cylinder Connection CGA 330, Calibration Certificate NIST, Made in the USA