BOL4 is short for Bolbbalgan4 (Korean: 볼빨간 사춘기 ). Their official English name is Blushing Youth, but most English-speaking fans still call them BOL4. They were formed in 2016 by Shofar Music and appeared on Superstar K6 in 2014. Originally a duo between Ahn Ji-young and Woo Ji-yoon, BOL4 is a solo vehicle for Ahn Ji-young as of April of 2020. As of 2024, BOL4 is currently signed to King Records.