Lifetime's smooth wall liners are your most economical choice. Strong and flexible, these liners are fully covered under Lifetime's warranty. Smooth wall better for wood burning, because creosote has a harder time sticking to it's smooth walls. Smooth wall Liners help gas and smoke exit efficiently and not through the house. All Sizes Available! Kit includes: Liner, Tee connector, Tee cap, Top plate, and Rain cap. To be used with: wood, pellet, gas, oil, and coal burning appliances. Note: The sizes given are outside diameter of the liner.