Also called kneaded rubber, this type of eraser is pliable and can be molded sort of like a stiff clay. It picks pigment off paper without leaving "crumbs," and can be re-kneaded to absorb graphite.
Since you can shape kneaded erasers into a point, they are good for erasing fine details. But because the rubber can become sticky after a lot of use, it's not the best choice for erasing large areas.
According to instructor Patrick Connors, "The ideal way to use it is not to rub, but to press, rotate and pull the eraser away from the paper. With these erasers, you also need to periodically pull and fold the eraser, kneading it."
Also available in boxes of 27pcs.