Aluminum is the preferred material for gas stoves and fireplaces, but it should never be used to line a wood or pellet stove. Aluminum liners can be used to line a traditional masonry or a class-A chimney. If venting a direct vent stove or fireplace into a chimney, you will need co-linear (two liners side-by-side) as one liner will serve as fresh air intake, and the other to exhaust your gas stove or fireplace. If you are venting a gas stove into a chimney, the national gas code and Maine fuel board do not permit using the air space around the liner to serve as the fresh air intake (despite the fact that some stove manufacturer's do). If you would like to install a free-standing gas stove into your chimney, Mazzeo's advises installing a B-Vent gas stove, such as a Jotul GF 300 Allagash or a Jotul GF 400 Sebago, which takes it's combustion air from the room, not the chimney, and uses only a single 4" aluminum liner for the exhaust. Whatever liner you need for your gas stove, Mazzeo's can help you find it!