SISTAR19 (씨스타19) is the first sub-unit of a girl group from Seoul, South Korea, 씨스타 (SISTAR), composed of members Bora and Hyolyn. The 19 is used to represent the girls maturing into women, as well as the innocence of being 19. After the announcement on April 27th, SISTAR19 released their MV Teaser on April 29, 2011 and the music video on May 2, 2011. They released their digital single, titled "Ma Boy", on May 3rd.