Industrial Scientific 1810-9177 Equivalent by GASCO Calibration Gas 18% Oxygen, 100 ppm Carbon Monoxide, 25 ppm Hydrogen Sulfide, 50% LEL Propane, Balance Nitrogen contained in a 58L Liter Disposable Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA