Tier1 PAS-1581 Replacement Pool and Spa Filter fits systems that use 5 7/8-inch diameter by 10 1/2-inch length filters. Tier1 Pool and Spa filters will protect your investment engineered to outperform the competition and exceed your expectations. Featuring high durability filter fabric that maintains strength even when loaded with sediment, a tighter porosity and denser weave to capture more contaminants in less time, and a high strength, high flow core designed to support the filter while providing industry excellence.