3" Downpipe and o2 housing

[ZDA1728]

Will a punishment racing 2.5 inch o2 housing fit on a 3 inch downpipe?

Nevermind Im almost positive all 3" downpipes have a 2.5" inlet

 

[Dsmkauai]

Most have a 2.5" flange and then either bump up to 3" or after the flex go to 3"