34es-416 200 PPM Carbon Monoxide 50% LEL Methane 20 PPM Hydrogen Sulfide 18% Oxygen in Nitrogen contained in a 34 Liter Factory Refillable ecosmart 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