GASCO Calibration Gas 116L-314S-NO2 60 PPM Carbon Monoxide, 2.5% methane (50% lel) 10 PPM Nitrogen Dioxide, 15% Oxygen Balance Nitrogen Contained in a 116L Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA