This Cap size is standard with 5-1/2" Block Design #6 and Casing Design #74, as shown, and fits 5" door and window Casing. Different Casing and/or Block designs can be specified below. Overall height is 8-1/2". Overall lengths of 28 inches or less are the same price. Each Door & Window Cap is made with "returned" ends; that is, the Moulding profiles continue on each end.
When installed, the square Blocks at either end of the Cap should center on vertical Casing on either side of your window or door. (Study Casing & Block Installation Overview and #5452 Usage Photo). Also, Blocks should be 1/2" wider than the Casing below them. Therefore, length B (see drawing above) should be 1/2" more than the overall width to outside edges of your vertical window or door Casing.
Length A is 2-5/8" more than B. When ordering, please specify overall length A.Example: If overall width to outside edges of window or door Casing is 36", length A will be 36" + 1/2" + 2-5/8" = 39-1/8".