With our Nesting Stovepipe the smallest piece fits inside the next larger piece and so on. Pieces must be removed and stacked in reverse order for use. The pipe set is 1″ bigger at the top than at the bottom. Joints fit inside of piece below, preventing creosote from leaking out. The pipe set has 5 pieces that are 22″. Our Scout pipe set has 6 pieces that are 14″ long. The stovepipe size is determined by the size that fits into the stove. For example, if the hole in your stove is 5″ (which is standard), then you will need a 5″ stovepipe.