Have used these for years for illustration work combines with oil based metallics as a resist. There is nothing to compare with the beautiful brilliant colors that have a unique depth of their own, unlike any other media. There are 4 edges, which allows you to do very fine work and color larger areas as well. They don't work that well for very large areas of color if you want it to be perfectly even. They also don't last that long if you are working with them and don't last indefinitely if they are sitting in a drawer, they will dry out. They are non-erasable. The colors will fade in sunlight, so I tell clients to treat the artwork as they would a color photograph. They are also expensive in retail stores, as much as 3.99 apiece. This is a great price on Amazon, so be sure to stock up.