1810-2343 Industrial Scientific Calibration Gas Mixture Equivalent by GASCO 25%, LEL Pentane, 25 ppm Hydrogen Sulfide, 200 ppm Carbon Monoxide, 20.9% 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