ALVINÂ® Penstix Drawing Marker Set...A unique high performance marker that produces crisp sharp lines for freehand drawing or for use with a straightedge. The dense India Ink quality black ink will not bleed through most papers and is perfect for technical drawing sketching fine art lettering and illustration â any project that demands high quality results. Favoured by cartoonists worldwide. The durable plastic fibre nib will not clog. Available individually in three line widths (0.3mm 0.5mm 0.7mm) or as a set of three. Penstix now include a convenient pocket clip and a ribbed cap that fits snugly on the barrel.