Iron Armour Seal
Name
Kanji	鉄甲封印
Rōmaji	Tekkō Fūin
Literal English	Iron Armour Seal
English TV	Iron Shell Seal
Debut
Manga	Chapter #408
Anime	Naruto Shippūden Episode #142
OVA	Naruto Shippūden: UNSG anime cutscenes
Appears in	Anime and Manga
Data
Classification	Fūinjutsu
Class	Supplementary

This is the fūinjutsu that was used to seal Gyūki into Killer B, which takes the form of the kanji for "iron" (鉄, tetsu) on his right shoulder. Not much 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 contained Kurama inside of Naruto Uzumaki.^[1]

Trivia

• In the manga, the seal is depicted as being black. In the anime however, the seal is blue.

References

1. ↑ Naruto chapter 496, page 7