GASCO 467 Calibration Gas, Carbon Monoxide 100 PPM, Methane 50% LEL, Hydrogen Sulfide 60 PPM, Oxygen 13% Balance Nitrogen contained in a 34 Liter Factory Refillable ecosmart Disposable Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA