1993 Select Dufex Insert Promos is a set of baseball cards from 1993 that was back doored into the secondary marketplace when Pinnacle Brands went bankrupt. Unlike many other promo sets, the cards were not released to hobby stores or media members prior to the release of the 1993 Select baseball card set. The cards appear to be Proofs of the Chase Stars, Chase Rookies and Aces insert sets in 1993 Select. The key difference is that the backs are completely blank. The card may have been test cards for the Dufex printing technology. It is unknown how of these cards exist or what the full checklist could be.