S1 Type Filter Cartridges: S1 type filter sponge for Intex Pure Spas, air bubble and water jet filters. Compatible with Intex 28604 and 29000 filter pumps. We recommend changing it every two weeks to achieve a better filtration effect and keep the pool cleaner. The pool filter cotton is made of premium polyester fiber, strong and durable. High-Efficiency Filtration: Captures particles and sediment and improves biofiltration. Good elasticity, high traction, fast dust filtration, high dust filtration rate. With this filter, you can enjoy a safe and healthy massage spa. Recommended use: We recommend changing it every two weeks to achieve a better filtration effect and keep the pool cleaner. Scenarios: Our washable foam filters are suitable for S1 and most pool filters on the market, keeping swimming pools, aquariums, and spas clean.