Biosystems 54-9046E by GASCO equivalent Calibration Gas, Carbon Monoxide 50 PPM, Methane 1.25%Vol = (50% LEL) Pentane simulant, Hydrogen Sulfide 25 PPM, Oxygen 18%, Balance Nitrogen contained in a 58L Liter Disposable Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA