[The-Cardfather]

I recently purchased a 2003 Donruss Career Stat Line card of Mike Piazza.

I understand that the Career Stat Line cards were issued as a parallel to the regular-issue Donruss set.

My question is:
How were they issued?

As a stand-alone set issued in packs or as a complete set?
As inserts in the regular-issue Donruss packs or complete set?
As inserts in another set?

Somebody please help!!!