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 9 3/8 in Material Plastic Compatible Register Height 9 3/8 in Compatible Register Width 9 3/8 in Duct Size 8 in Cap/Collar Material Plastic Product Type Register Boot Damper Type None Standards UL 2043 Classified