Industrial Scientific 1810-9181 GASCO Equivalent Calibration Gas: 25% LEL Pentane, 18% Oxygen, 200 ppm Carbon Monoxide, 25 ppm Hydrogen Sulfide, 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