Frost King 21 37 in. W Steel Adjustable Window Screen (Pack of 12).Window screen ventilators metal rail adjustable width 21 inch to 37 inch height 10 inch. Window screen ventilators metal rail adjustable width 21 inch to 37 inch height 10 inch. 10 inch x 21 inch 37 inch, louver metal rail extension window screen, extends from 21 inch to 37 inch, painted metal rails and varnished wood ends, extra sturdy tenoned corners keep screens square, zinc plated nails. Doubles as a screen and vent letting fresh air in and