Downspouts should match the type of gutter being installed. Fascia gutters only have a 2-1/4" wide bottom so a 3-inch x 4-inch downspout would not be the best choice for size. Aluminum downspouts are made up of three different components. Two elbows and section of pipe at the top called a leader, the main downspout pipe and an elbow at the bottom. The downspout is straped to the home using matching material to help it blend in.
Steel downspouts do not require elbows as the steel pipe is notched and bent to the downspouts shape. The bends are then soldered or riveted and sealed together. These bends tend to be more sharp or have tighter turns then the aluminum style, which may cause the downspout to become clogged more easily.
Available materials are Copper, Aluminum, Bonderized, Galvanized or Steel. Available shapes are Round, Round Corrugated, Rectangular Smooth and Rectangular Corrugated. The round shapes come in 2-inch, 3-inch or 4-inch, while the rectangular come in 2-inch x 3-inch and 3-inch x 4-inch.