Suburban Mfg Furnace Duct Cover Plate For 4in Duct. It is compatible with Suburban's 4" furnace ducts. Includes a 90 day limited warranty. Features of Suburban Mfg 50733 Furnace Duct Cover Plate For 4in Duct Designed for use with RV furnaces Compatible with Suburban 4" ducts Includes one duct cover plate per package 90 day limited warranty Package Contents: Suburban Mfg 50733 Furnace Duct Cover Plate For 4in Duct Suburban Mfg 50733: Furnace Duct Cover Plate For 4in Duct