The Poké Ball (モンスターボール, Monsutābōru?, Monster Ball in original Japanese language versions) is a spherical device used by Pokémon Trainers to capture wild Pokémon and store them when not active. The balls convert a Pokémon into energy upon contact, suck it inside, and close automatically. Stronger Pokémon are able to struggle and possibly break free, while those that have been weakened are easily captured. The Poké Ball, not in use, is the size of a golf ball and with the press of the central button, enlarges to the size of an orange. The Pokémon is released for battle by throwing the ball, and when retrieving a Pokémon, a beam of red colored light will convert the Pokémon into energy and retrieve it. The Pokémon Voltorb and Electrode are often mistaken for Poké Balls.
Various Poké Balls exist. The basics which were introduced in Generation I are the Poké Ball, Great Ball and Ultra Ball, which are progressively stronger, and the Master Ball, which has a 100% success rate against any Pokémon that can be captured. Other specialized balls include the Timer Ball, which becomes more effective the longer the battle progresses, the Net Ball, which has a better chance of catching Water and Bug-type Pokémon, and the Dusk Ball, which is most effective at night or inside caves, among others.