GASCO Calibration Gas 44es-414WI Mixture 300 PPM Carbon Monoxide, 10 PPM Hydrogen Sulfide, 0.81 % Pentane (58 % LEL), 15 % Oxygen, Balance Nitrogen Contained in a 44L Liter ecosmart Factory Refillable Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA