[BR3W CITY]

note that it says "50psi max pressure" (i misquoted and said 25psi). Technically our fuel systems run at a higher pressure than that. I understand that the fitting will "probably hold", but still probably not the greatest idea.
Best to either a. use a sleeve and tube nut and make a 37* flare on the line, then attach using regular AN fittings...but you need a 37* flare tool for this.
b. go from 3/8 tube nut ->female to female coupling-> 3/8 male to -6 AN adapter. This leaves you with all threaded mechanical connections, which will hold well over and psi the rail would ever see.