RAE 600-1051-000 equivalent by GASCO 301A Mix, 2.5% CH4 (50% LEL Methane), 50 ppm Carbon Monoxide, 18% Oxygen, Balance Nitrogen contained in a 34 Liter Disposable Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA