Inside the chunky aluminium barrel of each Pentel N50 permanent marker is quality Pentel indelible ink that writes smoothly on almost any surface. The Pentel N50 Marker features a durable permanent bullet tip, suitable for almost any surface, rough or smooth. It's heavy duty, with a tough aluminium barrel. The N50 bullet tip permanent marker is the UK's favourite permanent marker with a robust aluminium barrel and a bonded fibre tip that retains its shape. It will write on almost any surface, including cardboard, metal, wood, rubber, plastic and glass. The approximate line width is 2.0mm. Unlike most markers, which are alcohol-based, the N50 contains heavy-duty solvent-based ink, ideal for serious industrial use. It will write on wet or greasy surfaces where other markers fail, drying instantly and permanently.