From BR Bullpen
Despite its name, Eerste Klasse (First Class or First Division) is not the highest league in the Netherlands. Rather, that honor belongs to Hoofdklasse. Due to promotion and relegation, teams move in between the leagues as do players.
The Eerste Klasse used to be a sort of a hybrid league, it was both the league for the reserve teams of Hoofdklasse clubs (8 of them) and the league in between Hoofdklasse and Tweede Klasse (second Class) for regular main teams (12 of those). The reserves played a double competition amongst themselves and a half competition against the regular Eerste Klasse teams, the regulars that half competition against the reserves and one and a half competition amongst themselves. Regulars and Reserves were ranked separately of course, the reserves are not directly affected by the promotion/regulation system. Promotion to Hoofdklasse was not automatic for the regular Eerste Klasse champion, (reserve teams cannot be promoted to Hoofdklasse). The club has to be able to fulfill its franchise/license obligations in the Hoofdklasse and be willing to make the transition to the highest level to even enter the best-of-five promotion/relegation series with the bottom Hoofdklasse team. Relegation is automatic for the two main teams at the bottom at the end of the season; they are replaced by the champions of the Tweede Klasse A and Tweede Klasse B. As such the Eerste Klasse was the highest league to be reached by the regular promotion and relegation system in Dutch baseball.
In 2009 the hybrid league Eerste Klasse had been split in a Rookie League (for the reserve teams, allowing more interaction with the Hoofdklasse teams) and the Eerste Klasse for the regular teams. Eerste Klasse Champions for 2009 were the Almere Magpies, who then defeated RCH to get promoted to the Hoofdklasse, though not without problems with the KNBSB board, which was concerned about Almere's financial stability.
The Eerste Klasse of 2009 will be the Overgangsklasse (Transition League) in 2010, while the Tweede Klasse of 2009 will be the Eerste Klasse of 2010 (and 3e 2009 will be 2e 2010. Starting with 2010 "Eerste Klasse" will no longer indicate a (semi) professional league, but the highest amateur league in the Netherlands.
 Eerste Klasse Teams 2008