Tried searching but not finding the answer I'm looking for.

I'm trying to identify what's after the downstream O2 sensor above the transmission cross member.

Is it a secondary catalytic converter? It appears to go upstream O2-> Cat-> downstream O2-> cat or resonator?

Every diagram I've found just lists it as a whole assembly welded together not each part.

I'll try to attach a picture with it circled

 

Pretty sure it's a secondary cat. Sometimes you will see them advertised as an assembly with 2 per side...

 

Thanks. It's on a parts truck I was given and my state has become stricker on emissions so today I found out my new to me explorer is missing a third cat. I was hoping for a quick fix of just swapping one of these secondaries in but I just cut both out of this truck and they've previously been gutted... Bummer