CB Mass

CB Mass (Critical Brain Mass) was a Korean hip hop group featuring members Choiza, (real name - Choi Jae-ho), Gaeko (real name - Kim Yoon-sung) and Curbin. Choiza and Gaeko originally met in the sixth grade but before forming CB Mass they began an underground hip hop group named kod along with Sixpoint and ZASON, who joined in 1998. In the same year, Choiza and Gaeko met a fellow rapper Curbin and created CB Mass.

The group debuted in 2000 under Drunken Tiger's wing and released Massmediah to moderate success. In total they produced three albums: MassMediah in 2000, Massmatics in 2001, and Massappeal in 2003. They disbanded later the same year after a heated and public dispute where Curbin was accused of stealing money from the group. Their second album Massmatics was their most popular, with 120,000 copies sold in Korea.

At the height of their success however there were continuous rumours that they would break up and their last album added weight to this speculation with just Gaeko and Choiza appearing on most of the songs. In the first song of Dynamic Duo's first album Gaeko raps "He liked standing in front of mirrors than music/ He worshipped cash more than friendship/ What he left with us is only betrayal," in a barely concealed reference to Curbin. After CB Mass broke up, Gaeko and Choiza formed Dynamic Duo while Curbin announced plans to go solo but has not yet released any material.