Once per turn, during your Main Phase, if you control this monster on the field, you can equip it to your "X-Head Cannon" or "Y-Dragon Head" as an Equip Spell Card, OR change it back to a monster in face-up Attack Position. When equipped to a monster by this card's effect, that monster's ATK/DEF is increased by 600 points. (1 monster can only be equipped with 1 Union Monster at a time. If the monster that this card is eqipped to is destroyed in battle, this card is destroyed instead.)