GASCO Calibration Gas 900es-414-40 300 PPM Carbon Monoxide, 40 PPM Hydrogen Sulfide, 1.45% Methane, (29% LEL), (58% LEL Pentane Equivalent), 15% Oxygen, Balance Nitrogen Contained in a 900 Liter Factory refillable cylinder, For Use with Any and All Gas Detectors, Cylinder Connection CGA 330, Calibration Certificate NIST, Made in the USA