This light up Necklace uses a 3/4 diameter LED light that fades on and off in a bright shade of purple. It is powered by 2 CR1220 lithium cell batteries which are included and replaceable. The LED light in the Glowing light up Necklace is surrounded by a gorgeous silver filigree wish box. The light up Necklace hangs from a 18" silver chain. I have also included a replacement set of batteries.