BOESER EZ FLANGE PLENUM 21 X 20-1/2 X 36 Breadcrumb Home / Products / Parts / Installation Products / Sheet Metal Ductwork and Fittings / Sheet Metal Plenums Loading... Customer Part Number: 7052120 Brand: Boeser Sheet Metal Front: Out Shape: Rectangular Size (In.): 21 x 20-1/2 x 36 Sides and Back: In Top: Yes