Tetra Whisper Unassembled Bio-Bag Filter Cartridges by Tetra 26164 Large 12-Pack Easy to Assemble, Easy to Replace The Whisper Bio-Bag multi-packs come unassembled and offer economical pricing on larger quantities Three stage filtration Whisper bio-bag cartridges complete the Whisper power filter package for a clean, easy-to-maintain aquarium. The Whisper bio-bag multi-packs come unassembled and offer economical pricing on larger quantities.