To activate, twist backing clockwise. To deactivate twist counterclockwise.- Piece attaches magnetically. - To attach, remove magnet on back of the piece. Hold magnet behind shirt (or desired location) and attach piece on opposite side. Height .75 in, 1.9 cm - Width 1.25in, 3.2cm. LED colors Red and Blue Batteries: Includes 2 replaceable CR927 batteries.