To activate your LED Sequined Baseball Hat, remove the pull tab & press the button on the battery house. One size fits most; not recommended for extremely large heads. Dimensions (LxWxH): 11 in. x 6 in. x 4.5 in. LEDs: 6 White LEDs LED Functions: Flash, blink & steady lighting. Comes ready to use with 3 replaceable AG13 Batteries.