GASCO Calibration Gas 34L-411x-10SO2-20.9 Mixture Oxygen 20.9%, SO2 10 PPM, H2S 25 PPM, 25% LEL Pentane, 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