Have your birthday items on hand and ready to use. Add the LED Happy Birthday Necklaces to your party supplies. It’s imperative to have a party favor ready to give to all your guests who show up for their birthday celebration. Each inexpensive piece measures thirty-eight inches as a one size fits most. Simply activate by pressing the button on the battery pack and choose one of the three different cycles. Replaceable batteries are included for a convenient use. Comes packaged bulk in a pack of twelve pieces.