I know this will appear to be a dumb question to most of you guys in the know of things, but here goes..... What size exhaust tip would I need so that the tip will slide over the outside of a 2-1/2 dia. tailpipe? Again, sorry for the dumb question. Thanks guys.

Generally what you're looking for is a 2.5" tip with a slip on style. That means it will slip over a 2.5" pipe. Check summit, they have a million different ones available.

If I understand the question correctly you just look for a exhaust tip for a 2-1/2 dia. tailpipe

For example if you look at this catalog it tells you what size exhaust they fit.

http://www.ttiexhaust.com/Exhaust%20Tips/Tips.htm

So I am now to understand that any "slip on" style tip will be an I. D. (inside diameter) measurement and the tailpipe an O. D. (outside diameter) measurement. For examle:

Tailpipe 2-1/2 O.D.
Slip on tip 2-1/2 I.D.

Would this be a correct assumption?

Thanks for the replies guys .