Typical recommended rough opening dimensions for Merzon Industries products:

Patio Doors

Windows

Window Sizing

Windows and doors are generically sized in feet and inches from the outside looking in and always with the horizontal dimension followed by the vertical dimension.  Example: 5068 would be five feet even by six feet eight inches.

The net window dimension refers to the actual width and height of the window frame not including the nail fin.

The callout dimension, or order size, refers to the rounded number size of the window in feet and inches.

The rough opening is the dimension of the framed opening in a wall equal to the dimension of the window plus clearance for squaring, usually 1/4" per side except at the sill.  A vinyl window should be set directly on the sill of the framed opening.