As a filter does it job trapping dirt and sediment particles, eventually it expires, clogging with the trapped particles. This high quality pre-filter protects your UltraHome system, extending the life and effectiveness of the main filter unit. Think of it as an inexpensive insurance policy. And, it’s easy to change too. Less expensive pre-filters are spun fiber. Ours is the highest quality pleated fiber providing more surface area and increased capacity to trap and hold particles. The best protection at a great price.