Z-Metal Tank (SBCB-EN065) - Speed Duel: Battle City Box 1st Edition

Once per turn, you can either: Target 1 "X-Head Cannon" or "Y-Dragon Head" you control; equip this card to that target, OR: Unequip this card and Special Summon it. A monster equipped with this card gains 600 ATK/DEF, also if the equipped monster would be destroyed by battle or card effect, destroy this card instead.