Suitable for paper, fax and carbon copies. The highlighters are copy proof and have a twist cap for easy opening. Each pen has a ultra-soft chisel tip that is approximately 1 – 5 mm. Airplane-safe - they feature an automatic pressure equalisation system that prevents the highlighter from leaking on board an aircraft. Refillable with the Staedtler Textsurfer Refill Station. PP barrel and cap guarantee long service life.