IMPERIAL 4-in 30 Gauge Galvanized Steel Round Full Flow Duct TeeThis sturdy Imperial 4 in Tee is used to branch a main line or a branch line with a 90 degree angle. The full flow tee is ideal for use with heating and air conditioning applications, as well as, bathroom fans and kitchen vent applicaitons. It is designed to connect pipes of the same diameter, but a reducer increaser may be used to modify multiple pipe size connections if required (sold separately). This duct tee is made from 30 gauge galvanized steel