GASCO 116ES-411 Calibration Gas Mixture 100 PPM Carbon Monoxide 25 PPM Hydrogen Sulfide, [0.35% VOL] 25% LEL Pentane 19% Oxygen in 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