GASCO 355S Calibration Gas 300 PPM Carbon Monoxide, 2.5 % Carbon Dioxide, 1.45 % Methane, (29 % LEL), (58 % LEL Pentane Equivalent), 15 % Oxygen, Balance Nitrogen contained in a 552 Liter Disposable Steel Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection: TBD GAS Specific, Calibration Certificate NIST, Made in the USA