Industrial Scientific 1810-9155 Calibration Gas Equivalent by GASCO, 25% LEL Pentane, 18% Oxygen, 100 ppm Carbon Monoxide, 25 ppm Hydrogen Sulfide, 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 (GASCO PN 411-18)