This model is used if thicker glass (3/16" or 1/4") is requested, including laminated glass for sound reduction and/or UV protection. It is a stacked model, with a top panel, stacked on top of the bottom with an H-Mull in between, centered with the existing double hung meeting rail. It provides ease of removal for both top and bottom panels for cleaning or ventilation. A magnetic, interchangeable screen insert is available.