1998 Topps Tek - [Base] - Pattern 76 #21 - Roger Clemens
Courtesy of COMC.com
Topps Tek was a series of acetate cards with 90 background variations for each card in the set, and those 90 are doubled because each variation also had a Diffractor variation:
1998 Topps Tek - [Base] - Pattern 84 Diffractor #29 - Gary Sheffield
Courtesy of COMC.com
So for a completist player collector, they would need 180 of each card. 90 cards in the set, so that makes 90x180 = 16,200 cards for a "complete" set. Some years, the rookies were also numbered and they had gold parallels printed to /10. Fun oddball set.