Since 2006, the Champions Series is a series of tennis tournaments designed for former champion members of the ATP Tour. The Champions Series consists of tournaments played in select markets where top players of the sport compete in one-night, four-player events with two one-set semifinal matches and a one-set championship match played in one evening. Eligible players competing on the Champions Series have either held a Top 5 singles ranking; been a Grand-Slam singles finalist, or a singles player on a championship Davis Cup team during their ATP tour playing careers. The Champions Series allows one wild card of their choice at each event. The series is produced by Inside Out Sports & Entertainment. The minimum age to participate in a tournament is 30.