100 PPM CO, 1.25% Volume Methane (50% LEL Pent. equiv.), 25 PPM H2S, 19% O2 Balance Nitrogen Calibration Gas contained in a 34 Liter Factory Refillable ecosmart Disposable Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA