Eheim Power Diffusor 12mm (4004651).
The Eheim power diffusor supplies air to the outlet of the filter by venture. It is mounted on the end of the inlet hose, close to the aquarium water surface. The flow of water in the hose creates a vacuum and pulls air in via the pipe on the diffusor. The air is mixed with the incoming water and it is injected under the surface of the water by the pressure of the filter pump. For the Installation Kit 2