MSA 10058021 Equivalent by GASCO, 300 PPM CO, 1.45% Methane 2.5%, CO2, 15% O2, Balance Nitrogen contained in a 116 Liter Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder connection C-10 5/8"-18 UNF, Calibration Certificate NIST, Made in the USA