600-0050-004 RAE Calibration Gas Mixture Equivalent by GASCO 413 Mixture,Hydrogen Sulfide 10PPM, Carbon Monoxide 50PPM, Methane 2.5% (50% LEL),Balance Air (20.9 % Oxygen balance Nitrogen) 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