Material: ALUMINUM Assembled Product Length: 300" Assembled Product Height: 4" Assembled Product Width: 4" Diameter: 4" . UL listed and marked Tough 3 ply aluminum foil laminate Maximum operating temperature of 250°F Will not support combustion Smooth inner core for low friction loss Ideal for venting bathroom fans Not recommended for dryers For dryers use ducting approved to 285ºF -- BTD48 HH #3721-609 or TD450 HH #3721-636