AN fitting question

Do these need anything on the threads? O-rings or what not to seal? Or do you just tighten and let it go?
I have some on a fuel regulator and fuel filter.

No O rings needed. They seal due to the flare on the ends of the fittings.

Thanks, just wanted to be sure.

Yep, they are designed with a couple of degrees interference in the fit, seal up quite nice. Put
them on everything on my fuel system. Make it very
nice for disassembly as well.