TA/AAR mufflers from Accurate LTD have an option of a 2-1/2" inlet I.D. size for those that require this size for larger headpipes as when using headers or if a big block has been transplanted in the place of the 340. The exit size on the mufflers remain the standard 2-1/4" I.D. size for the exhaust tips. Hope this answers your question.
