GASCO 34L-403E 50 PPM Carbon Monoxide, 25 PPM Hydrogen Sulfide,1.62 % Methane, (32.4 % LEL) , (50 % LEL Propane Equivalent) , 18 % Oxygen, Balance Nitrogen contained in a 34 Liter Aluminum cylinder With a C-10 connection, For Use with Any and All Gas Detectors, Cylinder connection C-10 5/8"-18 UNF, Calibration Certificate NIST, Made in the USA