GASCO 34L-421-ISO | X06NI79CA340006 | Calibration Gas cylinder | 100 PPM Carbon Monoxide, 2.5% Methane (50% LEL), 100 ppm Isobutylene, 18% Oxygen Balance Nitrogen Contained in a 34 Liter Disposable Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA