Efficient for ecology. STAEDTLER develops clever product solutions that are not only environmentally friendly but also efficient for the user. Blocked tip: Even with exceptionally strong writing pressure, the tip of the marker remains blocked and cannot be pushed into the barrel. Suitable for paper, fax, and carbonless copy sets. High lightfastness: writing is still easily legible after years. Easy to refill with a refueling station. Ink-jet safe: all colors do not smudge inkjet printouts and handwritten text. Copy proof: violet and turquoise for originals to be copied. Twist cap for easy opening. Airplane safe: automatic pressure equalization prevents pen leakage in the airplane.