The PelletVent Pro Wall Thimble Air Intake Kit allows outside fresh air for combustion through the wall thimble without having to cut a second hole into the wall. Comes with an insulation ring to cut drafts where the pipe slips through the thimble. The 2" diameter, 18" length flex hose expands to 5'. Clamps included. Expands to 8 inch/ Can be used in US and Canada.