This stun gun has a built-in nickel-cadmium rechargeable battery and comes with an easy to use integrated charger. Simply plug the charger into the stun gun and then into an electrical outlet. The LED charge light will turn on. The stun gun may have a small charge when it arrives but you will need to charge it for 4 hours. After the initial charge and long periods of inactivity we recommend recharging the stun gun for 2 hours. Dimensions: 5 1/8" x 1 3/8" x 1 1/8".