Duct Start/Take Off Collar, Boot Style Speedi-Boot Hanger, Collar Diameter 4 1/8 in, Collar Connection Height 4 1/8 in, Collar Connection Width 13 3/8 in, Material Plastic, Compatible Register Height 13 3/8 in, Compatible Register Width 13 3/8 in, Duct Size 12 in, Cap/Collar Material Plastic, Product Type Register Boot, Damper Type None, Standards UL 2043 Classified