Rapidograph® pens are a superior grade technical pen that offers precise, uninterrupted line work for a number of applications. These pens work best on a smooth surface as textured surfaces may cause the finer nib sizes to skip. POINTS/NIBS: Each Rapidograph® pen features a stainless steel nib in one of 10 sizes from the hairline 6×0 (.13mm) nib to the large 4 (1.20 mm) nib. Replacement points are available for all pen sizes. Alternative tungsten carbide nibs are twice as strong as steel and are available in sizes 3×0, 00, 0. The pen also features a white plastic barrel with a refillable ink reservoir (pens do not come filled with ink), and a color-coded cap for nib selection. The double-seal cap is air-tight to keep the nib from drying out. Each pen is identified by a standard nib size or by its line width expressed in millimeters. Note: “nib” and “point” are terms used interchangeably but point sizes do not correspond to points in the point/pica system of typographic measure. A chart is available for the nib size, inch, and millimeter equivalent for each pen size in the pen care PDF.