GASCO 414X Calibration Gas, 1.45% vol. Methane (58% LEL Pent. Equiv.), 10 PPM H2S, 15% O2 Balance N2 contained in a 66L Liter ecosmart Factory Refillable Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA