Reusable foam box. Suitable for Bubble and Jetted Pure-spas. Replacement for S1 carton. Replacing the filter elements of paper filter is part of the daily maintenance of the pool. These cleaning and reusable foam filters will reduce your cost. The initial cost is slightly higher than that of paper filters, but the lifespan is longer. More durable than paper cartons, and it can be washed and reused multiple times. Size: 10.8 x 7.3 cm Center hole diameter: 4 cm Note: Allow 2 hours for the compressed product to fully expand Color: blue Material: sponge Package Contents: 16 x Filter Sponges Only the above package content, other products are not included. Note: Light and display differences may cause slight color variations between the image and the actual item. Measurement error allowance: +/- 1-3 cm.