Key Features Keeps water crystal clear and healthy Reduces Algae 1x Filter Cartridge and 1x Algaway pad included. Monthly Service kit - 3 x kits per pack Fits the PF4 Internal Filter The Interpet PF Service kits contains all you need to keep your PF Internal Filter clean and fresh every month. Each kit contains a sponge and carbon pad that can be easily replaced in your aquarium filter. It is important to replace your filter foams on a regular basis as this ensures crystal clear and healthy water for your aquarium fish. Each box purchased contains 3 x service kits giving you 3 months worth of supplies to keep your aquarium at its best. Fits the PF4 Interpet Aquarium Filter.