7803-030 GfG Calibration Gas Equivalent by GASCO 200 PPM Carbon Monoxide, 50% LEL Methane, 20 PPM Hydrogen Sulfide, 18% 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