Smooth Wall Double Ply Flex-All Chimney Liner is made from a single strip of 316Ti 0.006 in. stainless steel. Corrugated interlocked seam on the outside provides for maximum strength and flexibility. Smooth interior inner ply wall creates positive air flow that increases drafting by 20%, while eliminating creosote buildup. Unbreakable seem locks are leak proof, air and water tight Excellent choice for relining masonry chimneys. All propose, can be used with gas, wood pellet, oil or wood appliances. Applications include: fireplace inserts, furnaces, boilers, water heaters, gas and wooding burning stoves. Backed by a lifetime warranty.