Bayer 04 Leverkusen, officially known as Bayer 04 Leverkusen Fußball GmbH and commonly known as Bayer Leverkusen or simply Leverkusen, is a German professional football club based in Leverkusen, North Rhine-Westphalia. From Wikipedia
The first transfer window closed after major signings to register squads for the Club World Cup; the next window opens on June 16.