BD High Quality Downspout Pipe Roll Forming Machine Square The most common downspout for use with Style A, and Style D gutters systems.Collect roof rainwater and lead it to the rainwater pipe laid below the ground. The application of steel downpipe makes steel building integrity stronger, there are a variety of elbow and downpipe matching, more complex walls are also suitable. Common specifications for round tubes are 40mm, 50 mm, 75 mm, 90 mm, 110 mm, 150 mm, 200 mm, 250 mm,