Collector Size

Do they offer both? Usually collector size is dictated by the primary tubes.

Unless you plan to run 3.5 inch exhaust, the 3" collector with your small primary tubes will work fine.

I'm thinking about building my own set of headers so I can choose. I see some 1 7/8 tube headers have 3" while other have 3 1/2" depending on the car, so wasn't sure what is "better"