To activate your press the black button located on the back of the necklace. Set the Light Up Purple Paw Print Charm Necklace to a fast flash, a slower blink or still light. Dimensions: Paw Height: 3.18 in. Width: 3.12 in. Depth: 1.25 in. Necklace Length: 36 in. LED Colors: Purple Bead Necklace Color: Purple Batteries: Includes 3 AG13 Batteries and are replaceable for this item.