Do I need an AN Spacer for all firewall penetrations?

I am about to install an AN807-4D through my firewall for the Manifold Pressure line. Does this require an AN Spacer? my bigger question I guess is when does an AN fitting need a spacer?

Thanks,
Matt

I believe you will need a spacer/washer for the firewall - I did on the 10. The material is too thin for the Nut to contact the surface and snug up on the threads. The washer also helps to spread the load against the thin stainless steel firewall.