The seal itself takes the form of the kanji for "iron" (鉄, tetsu) and is usually printed somewhere on the jinchūriki's body: Killer B's right shoulder, and Blue B's chest. Not much else is known about the seal, besides the fact that it was stated by B to be of lower-quality and weaker than the Four Symbols Seal, which was used to seal Kurama inside of Naruto Uzumaki.
- In the manga, the seal is depicted as being black. In the anime however, the seal is blue.
- In the anime, the Five Elements Unseal appears to be strong enough to break the Iron Armour Seal.