Loading... Please wait...58L-404 100 PPM Carbon Monoxide, 2.5% Methane [50% LEL Methane], 25 PPM Hydrogen Sulfide, 20.9% Oxygen, Balance Nitrogen contained in a 58 Liter Aluminum Cylinder, Cylinder connection C-10 5/8"-18 UNF, Calibration Certificate NIST, Made in the USA