GASCO 50 PPM Carbon Monoxide, 25 PPM Hydrogen Sulfide, 1.62 % Methane,(32.4 % LEL),(50 % LEL Propane Equivalent),18 % Oxygen, Balance Nitrogen, in a 58 Liter ecosmart Aluminum cylinder, C-10 connection, For use with any and all detectors, Calibration Certificate NIST, Made in the USA