Galvanized metal lint trap for dryer boosting applications. Use when duct length between dryer and booster fan is less than 15 feet. Fits 4-inch duct. Features pull out door with view window, removable lint filter for easy cleaning and 1/2? flange for flush mount installation. This product is not designed to be installed inside of walls. It is recommended that you clean this unit several times per year and the lint trap needs to be accessible so you can do that.