Derwent Blender Pens are designed to use with pencils. They allow the artist to mix pencil lines, creating smooth, uniform colors, and are effective with coloured pencils and graphite. They come in a package of two sizes of 2 mm and 4 mm. Instructions: Apply on the pencil to make the shades more uniform. Layers of pencil can be overlaid if necessary. Use the fine tip for more precise areas.