GASCO Calibration Gas 650es-414-35 300 PPM Carbon Monoxide, 35 PPM Hydrogen Sulfide, 1.25% Methane, (25% LEL), (50% LEL Pentane Equivalent), 15% Oxygen, Balance Nitrogen Contained in a 650 Liter Factory refillable cylinder, For Use with Any and All Gas Detectors, Cylinder Connection CGA 330, Calibration Certificate NIST, Made in the USA