GASCO 34L-314a-NO2, Calibration Gas 60 PPM Carbon Monoxide, 1.45% Methane (29% LEL), 10 PPM Nitrogen Dioxide, 15% Oxygen Balance Nitrogen Contained in a 34 Liter Disposable Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA