The Katadyn Pocket filter has two plastic caps to protect the holes where it goes into the dirty water and where it leaves the filtered water. It may be interesting to make a small mark at the plugs for so always place them in the same hole and not dirty hole clean filtered water with dirty water Cap. It is a recommendation that Aitor has given to us. From the Katadyn House comment us that new models are already going to bring different plugs.
KATADYN POCKET Water Filter