The Staedtler felt pen contain a water-based pigment ink that dries quickly and is tamper-proof and indelible. It has a system for optimum ink flow and a refill system. The diameter is shown on the end of the felt pen. It is suitable for use with alphabet stencils. It has an aluminum finish and a rubber grip zone with anti-roll system, a safety cap with screw system and a chrome metal clip. This fineliner for writing, sketching and drawing can be left uncapped for 18 hours without drying up (Test ISO 554). Airplane-safe: automatic pressure equalization prevents pen leakage while on board aircraft. Long metal tip, ideal for use with rulers and templates. Pigment ink, indelible. Lightfast and waterproof ink. Erasable when used on tracing paper, no bleeding when highlighted. Sturdy metal clip. PP barrel guarantees long service life. 5 line widths available in black ink. Line width: 0.05 mm.