1810-6773 Industrial Scientific Calibration Gas Mixture Equivalent by GASCO 100 PPM Carbon Monoxide, 25% LEL Pentane, 5 PPM Nitrogen Dioxide, 19% 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