Having performed on M! Countdown and Music Bank, the four girls continued with their comeback stage on this week's MBC's Music Core. More than a year has gone by since Park Jung Ah and Seo In Young left the group to pursue their solo careers, and it has been one long wait for fans as Star Empire patiently scouted replacement members to join Ha Joo Yeon and Kim Eun Jung. Superstar K Top 10 finalist, Park Se Mi, joined the group 6 months ago, and Kim Ye Won rounded out the quartet, having just been unveiled earlier this month. After months of preparation, the new Jewelry makes its return with a brand new power 'locking' hip hop dance style and b-girls concept for their comeback single, 'Back It Up'. Check out their performance below!