Watch Fifth Harmony 'Flex' on 'Dancing With the Stars'

Fifth Harmony transformed the Dancing With the Stars ballroom into a reggae club during Tuesday’s finale episode with new single “All In My Head (Flex).” The all-female group had the stage crammed with backing dancers doing tight choreography.

The album version of “All In My Head” features rapper-singer Fetty Wap and is on the group’s upcoming second LP, 7/27….