The BiOrb Service Kit Six Pack Plus Replacement Airstone Bundle has the two most important for maintaining a BiOrb Aquariums. The Service Kit has the replacement filter cartridge, which should be replaced every month. We've included six service kits to cover a six month period. It also includes a small cleaning pad and water conditioner. The Airstone, which the air pump runs through to create bubbles, will get clogged over time and should be replaced about every six months. Suitable for ALL BiOrb, BiUbe, BiOrb FLOW and BiOrb Life aquariums.