Just wanted to share: these things are great for cleaning endmills. They’re a kind of putty-like material normally used by artists/illustrators to erase pencil marks from their work, so they’re specifically designed to be amazing at picking up small particles (like metal chips). Since they’re so malleable, they can get right around the flute edges and pick up everything, wherever it is. Unlike Blu-Tack (recommended by NYCCNC), they’re not an adhesive, so they’re really easy to get out of the endmill as well.
They’re also ubiquitous and dirt cheap.