GASCO 552l-331 | X04NI87CP550000 | Carbon Monoxide 50 PPM, Hexane 15% LEL, Oxygen 12%, Balance Nitrogen contained in a 552 Liter Disposable Steel Cylinder, For Use with Any and All Gas Detectors, Cylinder connection: CGA 590 Gas Specific, Calibration Certificate NIST, Made in the USA