RKI 81-0142RK-02 equivalent Calibration Gas by GASCO 5 ppm SO2, 25 ppm H2S, 50 ppm CO, 50% LEL CH4, 12% O2, 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