2008 Topps Moments & Milestones is a 189-card set, released exclusively to Hobby outlets, in April, 2008. The set consists of 144 veteran and retired players and 45 cards of 15 different rookies.
The set follows the same "mirrored" structure of the previous year's product. Each of the 144 veterans has multiple variations based on the player's statistical accomplishments. For example, Scott Rolen's card #73 has 21 different variations, one for each home run he hit during his 1997 ROY campaign. Like a mirror, each of the 21 cards is identical to each other, with the exception of a large numeral on the front side of the card. Each individual card is serial-numbered to 150 copies, but when all the different variations of each card are factored in, the production runs are much higher -- there are a total of 3,150 copies of the aforementioned card #73.
*Fun fact: Scott Rolen was the unanimous choice for the 1997 NL Rookie of the Year, however these cards were printed with the 2001 NL Rookie of the Year on the front.