【Wide Compatibility】: Compatible with water fountains from 2.5L stainless steel, 2L flower well with LED night light. Size: 10.5cm (diameter), 1.9cm (inner diameter). Please check the card slot size of your water well before purchasing. 【Effective Triple Cleaning】: The pet fountain filters replacement consists of a layer of cotton, activated carbon, coconut shell and ion exchange resin with ABS grids. It can effectively remove contamination, hair, heavy metals, odor, water and get better tasting water. Let your pet drink clean water. 【Easy to use】: Before replacing the pet fountain, the completely new replacement of the pet water fountain is completely smooth for remove excessive and scattered dust from the charcoal. Then install the cat fountain filter into the drinking fountain. (The cotton grating side is up). 【Fountain filter frequency】: Replace fountain catriages every 2-4 weeks to keep the water clean. If multiple pets use the fountain, a more common pet water fountain filter