Unique Fit: The only foam filter brand used to fit the ORSDA / Wopet Stainless Steel Pet Fountains | Fresh, Filtered Water: The replaceable foam filter catches hair and debris, keeping your cat’s water clean | Protect Pump: Replacement foam filter helps extend the life of your fountain pump by catching hair and debris before it reaches the pump | Easy to Replace: Easily removes when you clean your pet’s fountain' pump. Replace the foam filter for the water pump every 1-2 months to properly maintain your pet fountain | Change Suggestion: We advice you change the black foam filter of the water pump every 1 to 2 months to maximize the pumping cleaning effect.