Please educate me on exhausts

[toyotas4all]

Looking at the aftermarket parts thread I see

MAGNAFLOW Universal Performance Muffler - (p/n: 11264) - [Offset/Offset - 2" In/Out]

MAGNAFLOW Universal Performance Muffler - (p/n: 14851) - [Center/Center - 2.25" In / 4" Out]

Borla ProXS Universal Muffler - (p/n: 40346) - [Offset/Offset - 2" In/Out]

Borla ProXS Universal Muffler - (p/n: 40358) - [Offset/Center - 2.5" In/Out]

I know for sure I'm either going for Magnaflow or Borla. This isn't to say which one is better or not but rather how do I interpret all these measurements. Now here are my gazillion and one questions

What does Offset/Offset mean?

What does Offset/Center mean?

What does Center/Center mean?

I see that there are different diameters for in/out. What are the benefits for having a smaller diameter in vs a larger diameter out, or having them the same? What's the difference?

[FlawedLegacy]

Tip in the middle is "center" and the one towards one end is "offset"
In is the size of the pipe going into the muffler, Out is the size of the pipe coming out of the muffler.

[toyotas4all]

How about the different diameters? What are the pros/cons of each of those?

[FlawedLegacy]

depends what size pipe you have coming in and the tip you want on the end.

I have this one and LOVE IT

Amazon

Amazon

install was super simple as well!

[SuperchargedMR2]

I have the Borla 2" offset/offset & it works great. I checked with many muffler shops before buying & they pretty much all recommended the 2" over the 2.25" for the 1.8L engine. I've never regretted it once, I love it!

[Fatty_Ong]

Part number for Borla bolt-in rear section is 11795.