Complete your Whisper Power Filter package with the Whisper Power Filter 40 Refill. These Whisper Bio-Bag Cartridges help you create a clean and easy to maintain turtle tank. These ready to use disposable single packs are filled with Ultra-Activated carbon, which remove odors, discoloration and waste particles. Change once a month for optimal cleanliness in your turtle’s habitat. These filters are single pack assembled and large sized.