Help! So I want to cut out my muffler and weld in a glass pack on my 2002 blazer LS .Pre existing pipes are 2.25" ID. What size glass pack do I need to get and are they flared already so they slip on? I can't seem to wrap my head around this!

 

I'd be surprised if those pipes were original as I'm pretty sure even 2" is considered an upgrade from stock. I would guess a muffler shop would be a good place to get advice if not some aftermarket muffler website.

 

Exhaust tubing is measured by OD, not ID. Sounds like you have maybe 2-1/2" pipe?

If you buy a 2-1/2" glasspack, it's made to slip over a 2-1/2" OD pipe.