Shinobi Gauntlet

The is a  developed by Katasuke of Konohagakure's Science Ninja Weapons Team.

Overview
As its name suggest, this tool is worn on the forearm. The user initiates one of their techniques before sealing them into a scroll. The scroll is then shrunken to pill-size and is put inside the Kote. Afterwards, they can release the scroll and use the sealed technique. To use an elemental technique, the user apparently needs to form the corresponding seal first. Because using the Kote doesn't require chakra, the user can gain an advantage in battle by releasing normally chakra-taxing techniques while saving their chakra or continuing to use techniques when low on chakra, thereby keeping the use rested and less-likely to endure exhaustion.

Trivia

 * Masashi Kishimoto thought of a tool like this since before Naruto began. However, he could never introduce it into the manga.
 * Kote also seemingly improves a technique's capacity, as Konohamaru's usage of Rasengan through this device allowed him to launch the normally-handheld technique a great distance away as a projectile.
 * Kote are currently banned from the Chūnin Exams by the Seventh Hokage, Naruto Uzumaki, stating it would be unfair for others who worked hard.
 * When Boruto Uzumaki used the Multiple Shadow Clone Technique with the Kote, the clones took the form of Boruto, rather than of the user who sealed the technique into the tool. It could also be that Boruto sealed the clones himself in that scroll from time to time, due to his limitations of only creating four clones at once.