1. fit: The cat fountain filter measures 2.99 x 1.69 inches, and the sponge measures 3.1 x 1.1 inches, making it compatible with most 67oz/2L, 101oz/3L, 108oz/3.2L, and 135oz/4.0L stainless steel pet fountains on the market. Please confirm compatibility with your cat fountain before . 2. Triple filtration system: The cat fountain filters are made of activated carbon, ion exchange resin, and nonwoven fabric, forming a triple filtration system. They effectively filter out impurities like hair and food residue, absorb odors, soften water, and improve taste and quality, ensuring your pet's health. 3. Easy to use: These replacement filters for pet fountains are simple to install and remove, saving you time and effort! Soak the filter and sponge in water for at least 3 minutes before use for filtration, and rinse thoroughly under running water. This helps keep the water fresh for longer. 4. Package includes: The set contains 24 individually wrapped and sealed cat fountain replacement filters and 24 sponges for convenient daily storage and use. Depending on your pet's drinking frequency and the number of pets, it is recommended to clean the filter weekly and it 12 times per month to maintain fresh, clean water.