54-9042E Biosystems Calibration Gas Mixture Equivalent by GASCO 50 PPM Carbon Monoxide, 1.62 % Methane, (32 % LEL) (50 % LEL Propane Equivalent), 18 % Oxygen, Balance Nitrogen contained in a 105 Liter Disposable Aluminum Cylinder, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA