The Lambro 3-1/4 In. x 10 In. to 6 In. round galvanized steel straight stack boot used for HVAC systems, floor registers or range hood venting. Installations consist of transitioning from round pipe or flexible insulated duct to rectangular stack duct. The stack boot is made of zinc-coated 30 gauge galvanized steel and provides advanced corrosion protection with pre-installed s-cleats. Install using sheet metal screws (not included) and it is recommended to seal seams with code approved mastic, sealant or duct tape (not included).