Using the 37 degree AN sleeves and nuts on aluminum lines requires a Parker Hannifin or another brand of a 37 degree flaring tool. I bought one when I owned maintained and flew my airplane years ago, those type tools are not cheap I have used a regular 45 degrree flaring tool(single flare oly on aluminum, not double ) on alumimum lines for the race car and got away with it, the trick is to NOT flare it all the way to 37 degrees, stop and slide the sleeve and nut up onto the aluminum line and get it close to being at the right angle and use the male end of the other fitting to do the final seating You can use regular brass or steel automotive 45 degree fittings also