 Following the addition of thirteenth member Kyuhyun, the group dropped the suffix "05" and became officially credited as Super Junior.The re-polished group's first CD single "U" was released on 7 June 2006, which was their most successful single until the release of "Sorry, Sorry" in March 2009, which helped them achieve global success.In April 2008, Choi was put into seven-member sub-group Super Junior-M, a Mandopop subgroup of Super Junior for the Chinese music industry.