BtoB 4U (Korean: 비투비 포유; stylized as BTOB 4U) is the second official sub-unit of South Korean boy group BtoB formed under Cube Entertainment. The sub-group consisted of members who have completed their military service Eunkwang, Minhyuk, Changsub and Peniel, who is exempt from conscription. They debuted on November 16, 2020 with the EP Inside, and made their debut stage on MBC Music's Show Champion on November 18.