GASCO Calibration Gas 58es-428-20CO2 60 PPM Carbon Monoxide, 20 PPM Hydrogen Sulfide, 2.5% Carbon Dioxide, 1.45% Methane (29% LEL), (58% LEL Pentane Equivalent), 15% Oxygen, Balance Nitrogen Contained in a 58L Liter ecosmart Factory Refillable Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA