GASCO 74L-428-20 Calibration Gas 60 PPM Carbon Monoxide, 20 PPM Hydrogen Sulfide, 1.45% Methane (29% LEL)(58% LEL Pentane Simulant), 15% Oxygen, Balance Nitrogen contained in a 74L Liter Disposable Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA