MSA 711076 Calibration Gas Mixture Equivalent by GASCO, 2.5% Methane, 300 PPM Carbon Monoxide, 15% Oxygen, 10 PPM Hydrogen Sulfide, 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