GASCO 509 Calibration Gas 15 PPM Acetylene, 15 PPM Ethane, 15 PPM Ethylene, 15 PPM Methane, 15 PPM Propane, Balance Helium contained in a 66L Liter Refillable Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA