Keep your aquarium clean and healthy with Top Fin's Element Filter Cartridges. These cartridges help absorb odors, pigments and chlorine with activated carbon. It's a great way to keep your aquatic friends happy and safe. Only at PetSmart. Features: Helps absorb odors, pigments, and chlorine with activated carbon, Easy to change Includes: (2) Filter Cartridges Intended For: Top Fin Element Filter Size: 2.1 in L x 1.9 in W x 3.7 in H Instructions: Rinse the filter cartridge under cool tap water to remove dust. To help maintain a healthy aquarium, change the filter cartridge every 3-4 weeks, or if water flow becomes obstructed. Remove the cartridge when medicating the water as the carbon will absorb the medications. Change out 10% of the water weekly or 25% monthly. Use a water conditioner (sold separately) every time you add fresh tap water to your aquarium. Never use soap, detergents, or cleaning agents while cleaning the aquarium or equipment as they can harm your fish. Caution: This is not a toy. Keep out of reach of children. Size: Large.