An activated carbon packed in a special quality tea bag material. In order to remove even volatiles with a boiling point near water, we have included a system of activated charcoal post-filtration for maximum purity. This is specially made to fit exactly into the carbon filter holder which goes right under the nozzle of the distiller. Water will then drip slowly through the activated carbon during distillation. The activated carbon we use is of extreme quality. Please do not use any other carbon, there are many different activated carbons available but most will not catch the volatiles we target here. To get maximum performance out of your post-filtration, you need to activate the carbon sachet before use. That is done simply by pouring some boiling water over it (use a kettle) and let it soak for 5 minutes. This also has the advantage of killing all bacteria which is important if you re-use the sachet. You can re-use a sachet around 3-4 distillations before loosing too much of the effect.