Record results in lab notebooks, fill in charts, draw graphs, mark recording paper and produce diagrams with these technical pens. They lay flat against rulers and flexible curves for accurate alignment. They are balanced for comfort in your hand. Instant writing, long storage time and dry-out prevention are supported by an airtight ring seal in the cap. The pens respond the moment they are touched to paper. Instant drying ink helps prevent smearing and bleeding. Line sizes are 0.2 and 0.4mm.