7th Gen Mega evolutions

[Rono6488]

Does anybody know can explain to me better about this mega evolutions? I understand I can use only one per battle, however when I use that stone for example if I use the blastoise mega stone one battle, will the stone disappear or can I use the mega stone for blastoise in another battle?

 

[Dragon]

Does anybody know can explain to me better about this mega evolutions? I understand I can use only one per battle, however when I use that stone for example if I use the blastoise mega stone one battle, will the stone disappear or can I use the mega stone for blastoise in another battle?

The stone won't disappear if you used one. Consider it like a held item for your pokemon. Once the battle is over, you can still mega evolve your blastoise again.