Most A-League clubs have teams in the National Youth League (Y-League), which runs in conjunction with the A-League as a national youth developmental and reserve league. All players in the youth teams are between the ages of 16 and 21 as of the start of the calendar year for each new season, while four over-age players from each of the senior teams also allowed to be selected. In addition, the W-League operates as the top division of women's league with affiliations to the men's competition.