Keep your pool water clear and clean with a Filter Cartridge (Type I) by Bestway. This replacement cartridge measures ?3.3''x3.5''/?8cmx9cm in and is designed for 330 gallon per hour (110-120V) filter pumps. They are easy to clean and sift dirt and debris out of your pool with your pump. Bestway recommends replacing them every 2 weeks for best results.