The standard (MOL) is a single panel, and is ideal for fixed windows where ventilation is not a major factor. This unit lifts out for easy cleaning. Large, undivided units can be provided, but the use of a (1-1/4”) glazing muntin can eliminate the need for heavier glass.
For very large or tall double-hung openings, the stacked unit permits the easy removal of all panels, for ventilation or cleaning. The (MMOL-ST) utilizes a (1-3/8" frame and has heavy extruded lift handles).