Click! The first modular system that cleverly links two pens together - use a single pen or connect two favorite colors together. This four pen set comes with a fold-out storage case that fits easily into a pocket and folds out to work as a handy holder on a desk. The pen body has an ergonomic three edge design, rubberized barrel, and is constructed from 88% bio-based plastic. Cap-off ink does not run dry even if the cap is removed for 2-3 days. The line width is 0.4 mm.