To order replacement RV shades that fit properly, first determine whether you want an inside mount (shade fits inside the window frame) or an outside mount (shade overlaps the window frame). For the 25-inch wide material with a 49-inch high window: if inside mount, order 25 inches wide by 49 inches high; if outside mount, add about 2 inches to each side and top/bottom, resulting in 29 inches wide by 53 inches high. For the 72-inch wide material with a 36-inch high window: inside mount requires 72 inches wide by 36 inches high; outside mount requires approximately 76 inches wide by 40 inches high. When ordering, double-check your measurements and mounting preferences, as custom shades are non-returnable. You can also select your preferred color and fabric options on product pages. Recommended products include Irvine Custom Shades in Pleated Night, Pleated Day/Night, and Valu-Line Night Roller Shade styles, all customizable to your exact dimensions and color preferences.