The Katadyn Carbon Cartridge is a light-weight water filter for clean drinking water. The filter fits on most drinking bottles enhanced with a wide opening. The filter comes with a bag of carbon to purify the water. You pour the carbon into the filter. Afterwards it is important you first flush water through the filter to remove any of the carbon left behind, before you start drinking. The filter reduces chemicals and improves the flavour and smell of filtered water. The filter has a capacity of approx. 200 litres. Afterwards you need to replace the carbon.