GASCO 413-12, 50 PPM Carbon Monoxide, 10 PPM Hydrogen Sulfide, 2.5 % Methane (50 % LEL),12 % Oxygen, Balance Nitrogen contained in a 34 Liter Disposable Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA