These one-of-a-kind ceramic necklaces are hand-made and glow in the dark. To charge, simply expose the necklace to any kind of light then see how it glows! The more it is charges, the longer it glows, up to 12hrs+. The cord is adjustable by pulling on both sides at the same time. One size fits all. They are non-toxic and utilize the most advanced material in glow in the dark technology.