RKI 81-0156RK-02 equivalent by GASCO Carbon Monoxide 50 PPM, Pentane 32% LEL, Hydrogen Sulfide 25 PPM, Oxygen 14%, 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