[😺【Compatibility】4 Pack cat water fountain filter replacement & 2 per-filter sponges perfectly compatible with 135oz/4L Dog Water Bowl Dispenser. 😺【 Triple Filtration Process】Dog water fountain filter replacement has 3 layer filtration system high density cotton non-woven fabric catch hairs and debris keep water clean; Activated carbon remove chlorine and odor purify and freshen water; Ion exchange resin filter heavy metals and improve taste. 😺【Pre-Filter Sponges】High density pre-filter pump sponges replacement can capture hair and debris and prevent them from entering into water pump extend the life time of your fountain pump. 😺【Replace Regularly】Suggest replacing pet water fountain filters every 2-4 weeks and replace sponges every 4 weeks please change it more often if your water fountain serve for multiple pets. 😺【Warm Tips】Before replacing the filter please soak the filter in water for 5 minutes and then rinse filter thoroughly with running water which will prevent carbon dust from shedding into water keep water clean and fresh.]