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Attack is boosted by 50% but the user is restricted to one move until they switch out, other than Mimic, Transform, and Sketch.
If the holder of this item uses Sleep Talk, it will select a random move for the first turn, and receive the boost as usual, but all subsequent uses of Sleep Talk or the move chosen by Sleep Talk will fail until the holder switches out.
Baton Pass counts as a switch as far as this item is concerned, and thus resets the move into which the holder is locked to no move.
If a Pokemon holding a Choice Band uses Pursuit against an opponent that switches out on the Pursuit user's first use of Pursuit since it switched in, the Pursuit user can select a new move next turn.
If a Pokemon with this item is Tricked or uses Trick, it can select a new move next turn, even if the item that was given to it is another Choice item. If, however, the Trick comes before they use a move, then the Pokemon is still locked in as though no Trick had taken place. For example, Alakazam uses Trick while holding a Choice Band, then Ursaring uses Swords Dance (in the same turn), Ursaring would have to use Swords Dance next turn, but Alakazam could do anything, even if it gained a Choice Band in return.