Adjusts from a minimum of 4 1/4" to a maximum of 7 1/4"wall thickness, and fits between standard wall studs. Toaccommodate thicker walls, the telescoping pieces can beextended up to 16' with a field-fabricated extension installed. Interior trim ring painted black. Must be installed with DuraPlus chimney pipe horizontally through the wall and extend a minimum of 2' into the room beyond the interior wall.