The DBX1000 Dryer Vent Box with snap on trim ring. Made of High Impact Polystyrene. The DBX1000 dryer vent box comes in two sizes 4" (For a 2x4 wall) or a 6" size. (For a 2x6 wall) This dryer vent box can also be used to down vent, just turn the box upside down and your done. The DBX1000 comes with a snap on trim ring which helps elimate repairs and saves you time.