Flange bolt question

[CRM]

I recently pulled out the crappy dual exhaust someone had previously put in, and I'm planning on going back to the Y pipe and single exhaust piping that the truck came with originally. While pulling the duals I discovered that the passenger side and driver side flange bolts were different lengths. I'm including a picture. My question is: are they actually two different sizes? I've searched all over for an answer but so far I've found nothing. Help me Obi Wan, you're my only hope.

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[fast 99]

Right/pass side should have had a heat riser valve.

 

[CRM]

It does and it has the longer bolts. Now it makes sense. Thank you brother !!

 

[CRM]

Another question....How tight do I tighten the nuts on the flange bolts? Until the spring is compressed all the way?