difference between old and new dynomax mufflers?

I just purchased a set of dynomax ultra flo welded mufflers for my duster from advanced auto. One is a new style box and the other in an older box. The salesman reassured me they were the same mufflers. They both say dynomax ultra flo welded on the box. My problem is they dont appear to be exactly the same. On the newer one you can see entirely through the muffler. The older you cant and it looks a little different. Did they change the ultr flos welded mufflers?