It is an iron rod whose size changes ''ruyi'' 如意 "as-one-wishes", once used by Da Yu to measure the depth of the flood waters destroying ancient China, which Wukong obtains from the undersea palace of Ao Guang, the Dragon King of the East Sea. It is immensely heavy; in modern measurements, it is slightly weightier than 7.5 metric tons. When it is not in use, Wukong shrinks it to the size of a sewing needle and keeps it behind his ear. It is often depicted as red and having gold bands near the ends. In other depictions, it is shown as a silver staff with golden ends, or as a solid gold or copper staff.
In popular culture
* Various characters in other manga and anime often wield an indestructible ''nyoi-bō'' staff based and modeled after the character Sun Wukong of ''Journey to the West''. Of the most popular of these depictions include of the '''' metaseries, the title character in the '''' television series, the Monkey King which can transform into a giant ''nyoi-bō'' in ''Naruto'', as well as . It is also one of the Precious of the ''Super Sentai'' series '''', although it is featured only briefly at the end of the final episode.
* In the video game Phantasy Star Online, one of the weapons is the Monkey King Bar that changes its size when used.
* In the , the character Kilik can wield the Jingu staff. In particular, Soul Calibur 3 has custom moveset called the "Soul of the Staff" which uses attacks where the titular staff changes length and width, with its standard size being estimated at a foot in length.
* In Defense of the Ancients, the Monkey King Bar is a powerful damage item that temporarily stuns opponents.
* In the movie , the quest of Jason Tripitakas is to return Ruyi Jingu Bang to the Monkey King and thereby free him.