585-000-043 IST-AIM Calibration Gas Equivalent by GASCO 50 PPM CO, 25 PPM H2S, 50% LEL Methane, 18% O2, 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