GASCO 429-16 100 PPM Carbon Monoxide, 75 PPM Hydrogen Sulfide, 2.5 % Methane (50 % LEL), 16 % Oxygen, Balance Nitrogen Contained in a 44L Liter ecosmart Factory Refillable Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA