The perimeter frame is constructed from the highest wet-strength 28 pt. beverage carrier board, securely bonded to the media pack. Support straps on the air-entering side are used in combination with a triple layer tri-ply support bar on the air-leaving side of the 2″ model to provide additional strength. The support straps and tri-ply support bar ensure integrity against turbulent airflow. The 2″ filter resists crushing and abuse, and provides excellent lateral stability for installation in side-access systems.
The 4″ model utilizes a two-piece die-cut frame with integral pleat spacers on the air-leaving side. Pleat spacing is controlled by straps bonded to the air-entering side, and the multiple rows of pleat spacers on the air-leaving side. The pleat spacers also ensure that the pleats remain open during use, maximizing filter life.