Size: The size of the fountain filter is 5" x 5" x 0.4" Measure your fountain and check if the filter can be built into your fountain before ordering. (Attention: Does not fit “Catit” fountain.) High quality: The replacement filter uses natural nonwovens, coconut shell activated carbon and ion exchange resin. It can catch pet hair and dust, effectively filter dirt and eliminate bad odors in water. Easy to use: Just put the raised side up and the flat side down, easy to install. Rinse the filter with water before use. Tips: We recommend changing the replacement filter every 2-4 weeks to keep the water clean. Hantoc always pay attention to the health of pet drinking water and help your pets love drinking water.