GASCO 650es-428-20SO2-10 Calibration Gas, 60 PPM Carbon Monoxide, 20 PPM Hydrogen Sulfide,10 PPM Sulfur Dioxide, 1.45 % Methane (29 % LEL),(58 % LEL Pentane Equivalent), 15 % Oxygen, Balance Nitrogen contained in a 650 Liter Factory refillable cylinder, For Use with Any and All Gas Detectors, Cylinder Connection CGA 330, Calibration Certificate NIST, Made in the USA