Question about the O-ring that is used in Federal power steering pumps where the high pressure hose fitting attaches to the pump. I have both an NOS pump rebuild kit and an aftermarket. Both kits include two different style O-rings that I assume are for the hose fitting. Do I use one or the other or both?

First pic shows the two different style o-rings.
Second pic shows the flat o-ring in place in the p/s pump. Seems like a perfect fit but why the xtra round o-ring?

Thanks