Master Flow Metal Pipe is available in a variety of common lengths, diameters and gauges to help make your next HVAC project a success. Round pipe can be used as a main trunk line or branch line, as well as in return air situations. It maintains the most efficient characteristics for airflow and is common throughout the country. A simple snap lock design and sturdy galvanized steel construction on Master Flow pipe creates a quick and secure installation that you can rely on.. Easy-to-install snap lock design. Crimped end for a secure interlocking fit. Galvanized steel construction. Always seal seams with building code approved sealant or duct tape. Can be cut to needed length with tin snips. Always insulate ductwork for greater system efficiency and comfort