Please note that this is the Narutopedia's article on the technique used by Sasori in the anime. If you are looking for the article on the technique used by Sasori in the game then you should head to Iron Sand Scattered Showers.
It is a gunshot-like attack which uses Iron Sand hardened into minuscule grains to attack simultaneously across a vast range. The bullets are so fast that they are difficult to see. The moment the user has finished preparing the attack, evading it becomes extremely difficult. Using the repellent force of magnetism, the speed of the bullets is rapidly increased after they are shot. Furthermore, the user can also use an attack pattern where the Iron Sand bullets are shaped into sharp needles, increasing their ability to wound or kill the opponent. Since the Iron Sand has a magnetic force and is also drenched in poison, defending against this technique is almost impossible. This technique is especially threatening to puppet users, since the puppets can be rendered immobile if the sand gets lodged into their joints. According to Sasori, this technique is unblockable.