Frost King RV/36H 36" Gry Vinyl Insert, 1-7/8" x 36", Grey 1-7/8" wide x 36" long: Fits one average door Replaces insert on Frost King aluminum thresholds Easy installation: Remove the old insert. With a pair of scissors, trim the replacement insert to the proper length. Start at one end with the grooved side facing up and press both edges of the insert in the threshold groove. Continue to press across the entire length.