These Kockney Koi 8mm - 4mm Airline Reducer Adaptor connectors are ideal used to join 8mm to  4mm airline, and ensure you can adapt your pipework to get the specific set up that you require.

There are a range of different connectors to ensure you can get this set up as you want, a T Piece, Straight Connector, 90 Bend and a reducer adapters ect.