The Filter Size: The round cat water filter is 4.13 inches in diameter and fits most cat fountains. Usage Details: Before use, soak the filter in water for 3-5 minutes, then rinse with running water. Prevents activated carbon dust from clogging the water pump of your cat's water dispenser. Triple Filter: Through triple filtration such as cotton layer, activated carbon and ion exchange resin, it can not only filter hair, heavy metals, but also improve the taste of water. Get your pets the cleanest water they can drink every day. Replacement Cycle Instructions: Depending on how often your pets drink water and the number of pets using the fountain, it is recommended that you replace the filter every 2-4 weeks. Each package has 6 sets of filters and can be used for 6 months. for 61oz/1.8L Cat Fountain Filter Replacement() (The actual product may have a slight color difference, which does not affect the use) Color: White & Blue Material: Activated Carbon, Cotton, Resin Package Contents: 6 pack * Cat Water Fountain Filter Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.