This seal is for the 2 piece Spartan window which was used on most 1950-1955 Spartan trailers. We have experimented with lots of different gaskets for these Spartan 2 piece windows. Our best results have come with a combination of using 2 different gaskets on the same window. This ribbed gasket which is part# CHW154 basically goes around the sides and bottom of the window and our part# CHW017 D-seal goes on the top of the window where the hinge is. The original seals must be removed from the window jamb. Care must be taken so that you do not bend the aluminum framing that holds the original seal. We suggest removing the entire widow from the trailer to install these seals. These seals will be put on the back side of the aluminum frame which holds the glass, or in other words, the opening portion of the window, so this surface must be clean and dry before applying new seal. For best results we suggest marking the location of the hinge on both the right and left side, then measure in 1” on both sides. This part# CHW154 seal will go 1” in from hinge all the way around the sides and bottom of window to the mark 1” in from the hinge on the opposite side. Then our part# CHW017 seal will fill the gap on the top of the window where the hinge is. The top gasket will need to be ordered separately. If you look at the photos that will help you understand. This is a high quality closed cell EPDM seal with heavy duty 3M adhesive. This seal is .50” wide and .312” tall. This seal is sold by the foot so you will need to measure your windows to figure out how much you need.