BW CG2-JX-34 equivalent by GASCO Calibration Gas, 100 ppm Carbon Monoxide, 2.5% Methane (50% LEL), 18% O2, Balance Nitrogen contained in a 34 Liter Disposable Steel Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection CGA 600, Calibration Certificate NIST, Made in the USA