R.ef, an acronym for Ruff Eazy Flava, is a South Korean co-ed group known for its contributions to the K-pop industry with a unique blend of hip-hop and R&B influences. The group initially made a significant impact in the mid-90s, during the formative years of the K-pop genre, as they brought a distinctive flair and culturally resonant sound that helped set the stage for future urban music trends in Korea.

After enjoying success with their initial releases, R.ef continued to evolve their music with albums like "Free Ruff Eazy Flava III" and "Second & Half". Their later work, such as "Back To The Black" and "Rave Effect", showed a continued dedication to pushing the boundaries of their sound while maintaining their signature style. Despite the changing landscape of the music industry and the rise of new K-pop acts, R.ef has maintained a loyal fan base, and their most recent releases demonstrate the group's ability to stay relevant and influential within the dynamic world of Korean music.