Designed and manufactured with precision for optimum performance. This is an easy-flowing, high opacity ink with excellent adhesion, suitable for tracing paper, vellum, drawing paper and lineboard. Calligraphy nibs, crafted from the finest stainless steel and hand finished for a smooth, precision inking edge. It's lightfast and suitable for all forms of reproduction. Ink has high color purity. Colored inks can be mixed with one another. Limited warranty: guaranteed for 2 years from original purchase date against defects in materials or workmanship. rOtring Isograph Technical Drawing Pen, Liquid Ink, 23 ml, Black.