To activate your LED Star Necklace, press the button on the back. With each click of the button, change your lights from a fast flash, to a slow changing rainbow, to all LEDs on at once, to red blink, blue blink & green blink. Height: 3.5 in. - Width: 3.5 in. - Necklace Lanyard: 31 in. LED Colors: Blue, Red and Jade Batteries: Includes 2 replaceable CR2032 batteries. - Weight: 0.10 LB