CG-Q58 BW Technologies Calibration Gas Mixture Equivalent by GASCO 100 PPM Carbon Monoxide, 25 PPM Hydrogen Sulfide, 2.5 % Methane (50 % LEL) , Balance Air (20.9 % Oxygen balance Nitrogen) contained in a 58 Liter Disposable Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA