The bulbs cost $57. In the hours before the versatile K-pop maximalists in BTS took the stage at Citi Field on Saturday night, fans were lining up by the thousands at stands throughout the Queens stadium, laying out not-insignificant amounts of cash for branded light sticks the shape of microphones and the size of Big Gulps.

Once in their seats, or out on the field, they held the lights — called Army bombs — aloft for the duration of BTS’s two-and-a-half-hour show, waving them in time with the music as various patterns were triggered via Bluetooth, turning the crowd into an ever-shifting sea of color.

Shows of severe devotion are the norm in K-pop, but even in that universe, the fervor generated by the seven members of all-boy BTS — RM, J-Hope, V, Jimin, Jungkook, Suga and Jin — is unusually intense.