Yesterday, we reported about SISTAR's first sub-unit 'SISTAR19', comprised of members Bora and Hyorin. The two have just released an MV teaser for their debut song, "Ma Boy", and it's already gaining considerable hype from K-pop fans worldwide. The '19' in their name became a topic of much discussion, as netizens debated over the exact meaning behind the number. Would it mean that their music is rated for those 19 and over, or does it allude to the innocence and energy of youth? The MV teaser reveals that the girls are aiming for a sexy, yet fun look, which they hope will translate through their music. Check out their video clip below!