GASCO Calibration Gas 116es-311-NO2-18 100 PPM Carbon Monoxide, 5 PPM Nitrogen Dioxide, 0.35 % Pentane (25 % LEL) 18 % Oxygen, Balance Nitrogen Contained in a 116 Liter Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA