This technique essentially hardens the hair on the user's head and shoots it at the enemy. The sharpened points of the hair can turn the target's entire body into a pincushion. The user can fire either individual strands of hair, or multiple strands can be wrapped together to create larger projectiles.
When in Sage Mode, Jiraiya can use a senjutsu-enhanced version known as Sage Art: Hair Needle Senbon (仙法・毛針千本, Senpō: Kebari Senbon). At the same time that Jiraiya kneads chakra and fires the hair needles, Fukasaku and Shima activate Jiraiya's hair roots, causing the hair to grow at an accelerated rate thus making limitless rapid-fire possible. The sheer speed of this technique makes it the fastest attack with the widest range in Jiraiya's arsenal.