Arena sets were produced in limited quantities with an estimated production run of 3,000 of each card (except Bob Lanier) for distribution at games. They were only produced for the following five teams:  Milwaukee Bucks, Los Angeles Lakers, Philadelphia 76ers, Dallas Mavericks, and the Boston Celtics (the same five teams that had SP team sets as part of the 1983-84 regular base set). Most Bucks Arena bags do not include the Lanier card as it was removed from the subset after he retired from the NBA. If your sealed bag has 9 cards, it is likely a rare bag with Lanier.