Basement window inserts come in standard and custom sizes
* There are 3 basic brands: Columbia, Kewanee, Monarch (look the same,but Different )
* Inserts are available in sIngle pane or dual pane insulated glass
* Steel buck frames have different outside drop downs for insert

The following Information is to help get the right product the first time:

Drop Down Depth on the steel buck frame: Primary Image
Kewanee drop down 5/8 to 1 inch
Columbia drop down 1/8 to 3/8 inch 
Monarch drop down 3/8 to 5/8 inch 

The drop down is measured from the outside, from top ridge on the bottom section of the steel buck frame. See 2nd & 3rd Image

Normal spacing between metal clips: See 4th Image 
Kewanee 19 inches
Columbia 19 inches 
Monarch 15-1/2 inches

NOTE 1: Monarch will fit all steel buck frame. However, you will see the black weatherstip when used with a Columbia insert. The visual weatherstrip can be removed

NOTE 2:  If not sure what you need, contact office.