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This is the small molding which is inserted in windows seals in some Vanagon models. It is actually a plastic piece which fades over time. If the window is installed you will need a special tool to install it. If window and seal are removed then it can be inserted without special equipment.
One item will be for one window (12'). You may have to trim the molding to the appropriate length. As an alternative you can replace the window seals with new seals, without the groove, which we usually have in stock.