103L-135A-1: 1 % METHANE (20 % LEL), BALANCE AIR (20.9% OXYGEN BALANCE NITROGEN) CONTAINED IN A 103 LITER STEEL CYLINDER C-10 CONNECTION Calibration Gas contained in a 58L Liter Factory Refillable Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA