In the Manga, the key is depicted to be an ordinary silver key with the crest of the Canis Minor, an image shaped like the Celestial Spirit itself, stamped on its bow. In the Anime, the key is still depicted as silver but is designed more intricately. The bow is hexagonal in shape and carries the crest of the Canis Minor with the blade of the key ending in a simple design, similar to other silver keys.
While in possession of the key, a Celestial Spirit Mage may be able to summon the Canis Minor Nikora by reciting the quote, "Open Gate of the Canis Minor! Nikora!". This summons Nikora, a Celestial Spirit mostly used for recreational purposes.