RKI 81-0160RK-02 equivalent GASCO 50 PPM Carbon Monoxide, 10 PPM Hydrogen Sulfide, 2.5% Methane (50% LEL), 12% Oxygen, 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