Active Aqua Replacement Pre-Filter for Pro Pump 275 and 500 Highest quality materials used to make high-end aquatic supplies Provide the best environment for your aquatic life with Danner products 100% designed and made in the Usa with quality goods Coarse polyester and foam offer biological filtration Carbon impregnated media offers chemical and biological filtration, all offer mechanical filtration For all mid range pumps, 250 GPH through 700 GPH Sleeve Small