585-000-044 IST-AIM Calibration Gas Equivalent by GASCO 100 PPM CO, 25 PPM H2S, 50 % LEL Methane, 20.9%, Balance Nitrogen, contained in a 58 Liter Disposable Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA