Exhaust Clamps Size Question
 

This may be a simple answer, but I want to be sure before I place my order. I'm looking to replace 2 of clamps that came with my LM2 exhaust (3" guillotine and 2.5" uni-bolt) with band clamps. I'm looking at getting preformed band clamps from Jegs. Do I need a 3" and a 2.5" or do I got a size smaller for a tighter fit? Thanks in advance.