The Techliner illustration pens have extremely fine polyacetal plastic nibs set in 0.5mm stainless steel sleeve for smudge-free inking. The disposable Alvin technical pens are ideal for precision drafting, free-hand drawing, or any design work. The pens water-based pigment ink is non-bleeding, waterproof, and fade-proof. They have acid-free, archival quality ink which dries quickly. The pens average write is approximately 4,400 ft.