Metric O Ring Hydraulic Fitting

Look Carefully and you will see an O-Ring in that fitting.  While this is considered to be the female fitting, (Nut)  The center is a male fitting that fits into a socket on the mating part.  This nut only needs to be snug enough to keep things lined up.  The torque is not needed to seal the connection.     The lines at this point are 1/2 inch and because we are only talking about pressures under 100 PSI there are no problems.   I know that some people use Aluminum AN Fittings However they are still flare type fittings just different angle of flare.  The information I got from the hydraulic shop will help you in your discussions with your hose supplier as they make what you need.   THEY ARE:

DIN Metric Thread size 15mm Light Duty  "15L" Thread size 22mm X 1.5 

Or DIN 2353 and DIN 3861