If a "Rescue-ACE" monster(s) is Normal or Special Summoned to your field, except "Rescue-ACE Fire Engine" (except during the Damage Step): You can Special Summon this card from your hand. If a monster(s) is Special Summoned to your opponent's field (except during the Damage Step): You can Special Summon 1 Level 4 or lower "Rescue-ACE" monster from your hand, Deck, or GY. You can only use each effect of "Rescue-ACE Fire Engine" once per turn.
