【Replacement Filter】The cat water fountain filter is made of high-quality activated carbon and a layer of natural cotton, high-density cotton can effectively isolate hair and other impurities in the water, comfortable and soft antibacterial. Activated carbon can help adsorb organic and inorganic substances in the water, effectively remove hair and heavy metals, and soften the water quality. 【12 Filters + 12 Sponges】This product contains 12 filters + 12 sponges. Filters and sponges are in the same package, the sponges are used to protect the pump and prevent hair in the water from entering the watercourse inside the pump. Extend the life of the pump. 【Keep Pets Healthy】It is recommended to replace the carbon filter every 2-4 weeks and the foam filter every two months to achieve the best results and keep the water quality fresh. 【Compatibility】 This product is suitable for various models of 2L/3.2L/4L water fountains. Don't worry about the size. As shown in Figure 5, it is very suitable