If held by an Audino, allows it to Mega Evolve into Mega Audino if its Trainer has a Key Stone. Each Trainer can only Mega Evolve one Pokémon per battle.
Unaffected by item negating effects (such as Embargo and Klutz). Item manipulating effects (such as Trick and Fling) cannot give Audino an Audinite or remove an Audinite from Audino.
Outside of battle
If held by an Audino, allows it to Mega Evolve into Mega Audino when it performs a Spectacular Talent during a Pokémon Contest Spectacular while its Trainer has a Key Stone. Audino will remain a Mega Audino until the Talent Round ends.