GASCO | 34L-404 | X04AI97CA34F020 | 100 PPM Carbon Monoxide, 50% LEL Methane, 25 PPM Hydrogen Sulfide, Balance Air contained in a 34 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