M-Flex™ liner is made from 316L stainless steel and is designed to reline existing chimneys or to be used in new construction. NATIONAL™ CHIMNEY manufactures M-Flex™ liner from the highest grade mill certified stainless steel alloy. It is made from a continuous strip of 7-ply stainless steel that is interlocked and crimped to produce a gas and watertight lining system of superior strength and durability. Its corrugated construction allows for expansion and contraction during heat up and cool down periods, removing any stress on the system. NATIONAL™ CHIMNEY M-Flex™ Liner, 35 ft Length, 6 in Width, 0.006 in Gauge, 316L Stainless Steel, Domestic