The Master Flow 4 in. x 3 in. Round Reducer is made of 26-Gauge, galvanized steel. It is used to transition from a 4 in. pipe to a 3 in. pipe in an HVAC system. It features hemmed collar edges for strength and a snug fit. This round reducer is suitable for most HVAC applications.Made of 26-Gauge, galvanized steelUsed to transition from a 4 in. pipe to a 3 in. pipe in an HVAC systemAlways seal seams with building code-approved sealant or duct tape not includedAlways insulate ductwork for greater system efficiency and comfort insulation not includedHemmed collar edges for a snug fit and increased strength