Armor Break is a Counter Trap Card.
Trap Cards are normally Set first and can be activated on a later turn, often in response to an action.
On the current TCG and OCG Forbidden & Limited lists tracked here, Armor Break is Unlimited.
YGOPRODeck lists Armor Break for these formats: GOAT, OCG GOAT, Duel Links, Common Charity, Edison, TCG, OCG, Master Duel.
A listed print of Armor Break appears in Ancient Sanctuary (AST-055) at Short Print rarity.
Among markets shown on this page, the lowest listed snapshot for Armor Break is about $0.06 on Cardmarket (prices change frequently).
