The Pokémon Organized Play promotional series was conceived as an extra incentive for players and collectors alike to participate in Pokémon leagues and Pokémon Organized Play programs. Instead of a single promotional card available at an event, it was a promotional set. Pokémon USA announced with the release of POP Series 1 that they planned to release a new series on a regular basis every six to twelve months. Each series would be exclusive to POP for six months, making league and various POP programs the only way to obtain the unique cards for a limited time. The cards are available in 2-card booster packs, with the odds of finding a rare card extremely low and collecting the entire set very difficult, a further incentive for people to continue playing the game.