600-0050-001 RAE Calibration Gas Mixture Equivalent by GASCO, 50 % LEL Methane, 20.9% Oxygen, 25 PPM Hydrogen Sulfide, 50 PPM Carbon Monoxide, 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