Dimensions: 10.8 x 7.3 cm. Center hole: approximately 4 cm. Designed for filter pumps 28604 and 29000. The swimming pool filter cotton is made of superior quality polyester fiber, strong and durable. Keep the water fresh: This massage pool filter keeps your jet spa massage water clean and fresh. It applies to most massage pools, with this filter, you can enjoy a safe and healthy massage spa. Convenient and durable: The pores of the swimming pool filter sponge are evenly distributed, which can effectively filter sediment and particles and prevent the accumulation of sediment. Save Time and Cost: These washable and reusable sponge filters can save your cost. We recommend changing it twice a week to achieve better filtration effect. Washable sponge: should be cleaned and replaced regularly, for maximum effectiveness, this massage pool filter should be cleaned weekly and replaced at least once a month.