CRL Zipper Pile Weatherstrip is a full density, high performance, water-resistant pile woven to a unique zipper tooth design polypropylene backing. The zipper tooth design allows the pile to easily snap into the extrusion slot from above rather than having to slide the pile in from the ends. Whether it's being used in manufacturing or retrofitted, the application is much easier and faster. It even works if the slot is slightly off size. Zipper Pile can be used to retrofit aluminum, vinyl, fiberglass or wood T-slots without the need to take the complete window or door sash apart. The double center fin provides a true weather seal, compared to other piles without a fin suited for vibration reduction and pest control only.