Tetra Whisper Assembled Bio-Bag Filter Cartridges Small 6 Total Filters (3 Packs with 2 Filters per Pack) Tetra Whisper Assembled Bio-Bag Filter Cartridges Small Color-coded packages for ease and accuracy in selection Convenience of being pre-assembled Filled with Ultra-Activated carbon, removing waste particles, odors, and discoloration Keeps water crystal clear