Options include: either a solid inner wall or a perforated inner wall. The perforated inner wall is for sound absorption and is used for applications like libraries, performing arts building, theaters, or such. Variations of composition include: galvanized, aluminum, stainless, PCD, carbon steel.
Dual wall is pretty endless on its size also (square) and (round) although round to not be smaller than 3” ID and not larger than 54” OD however we always can get bigger if required