The QUANTAPANEL 704-DH Architectural Low-e Storm Window installs on the exterior of an existing window on the blind stop. The attachment flange is positioned perpendicular and in the center of the box-beam frame, providing an exceptional, low profile, more fully integrated installation. This 2-track system has a removable upper sash and removable screen in the outer track, and an inner sash that opens vertically to adjustable heights to allow for fresh air ventilation. All sashes remove to the interior for cleaning and maintenance. The low-profile design integrates with the existing window providing an unobstructed view of the existing primary window. An optional interior handle on the lower, operable sash provides simpler operation when opening and closing the window. The QUANTAPANEL 704-DH Architectural Low-e Storm Window is available in standard or custom colors (185 colors to choose from)!