Activated carbon discs improve the palatability of water by removing chlorine, taste and odour. This 3 pack of carbon discs are only compatible with LifeSaver Libertybottles. This is a 3 pack of carbon filters that help remove scents and unpleasant tastes when you are purifying water using a LifeSaver liberty purification system. Each carbon disk will work on 500 litres of water, so this 3 pack when added to the one that is installed in the bottle when you buy can help clean 2000 litres of water in total.