The Master Flow 4 in. x 4 in. x 4 in. Wyes are made of 30-Gauge, galvanized steel. They are used primarily to transition from 1 pipe to 2 pipes in heating and air conditioning applications. They are easily installed with sheet metal screws not included. The joints have a maximum temperature rating of 390F.30-Gauge, galvanized steelUsed primarily to transition from 1-pipe to 2-pipes in heating and air conditioning applicationsCan be installed with sheet metal screws not includedMaximum temperature rating of 390F