600-0050-007 RAE Calibration Gas Mixture Equivalent by GASCO, 50 PPM CO, 2.5% (50% LEL) Methane, 10 PPM H2S, 18% O2, Balance Nitrogen contained in a 34 Liter Disposable Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA