Speedi-Boot SBH-4106 NB 4-Inch Width by 10-Inch Length to 6-Inch Diameter 90-Degree Register Vent Boot with Adjustable Hangers Adjustable telescoping hanger arms that can be shortened as well Foam gasket seals air tight at installation to back of sheetrock Dust and debris cover preventsconstruction contamination Mud ring prevents gaps between the boot and sheetrock Dust and debris cover provides a plug for HVAC pressure testing