In addition to the conventional wood pencil, a number of other pencils are widely used. In the early 1880s, the search for a pencil that didn't require sharpening led to the invention of what has variously been termed the automatic, propelling, or repeating pencil. These instruments have a metal or plastic case and use leads similar to those found in wood cased pencils. The lead, lodged in a metal spiral inside the case, is held in place by a rod with a metal stud fastened to it. When the cap is twisted, the rod and stud move downward in the spiral, forcing the lead toward the point. The early twentieth century saw the development of colored pencils in which the graphite core was replaced by a combination of pigments or dyes and a binder. Today, colored pencils are available in more than 70 colors, with 7 different yellows and 12 different blues. However, the cedar-casing lead pencil—manufactured at a pace of 6 billion per year in 40 different countries