Alvin Penstix are unique high performance markers 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 – any project that demands high quality results. Favored by cartoonists worldwide. The durable plastic fiber nib will not clog. Alvin Penstix Pens are available individually in three line widths (0.3mm, 0.5mm, 0.7mm) or as a set of three. Penstix pens include a convenient pocket clip and a ribbed cap that fits snugly on the barrel.