CG-Q34-4 BW Technologies Calibration Gas Mixture Equivalent by GASCO 2.5% Methane (50% LEL), 18% Oxygen, 25 PPM Hydrogen Sulfide, 100 PPM Carbon Monoxide in 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