Airplane-safe - automatic pressure equalization prevents pen from leaking on board aircraft Ergonomic triangular shape for relaxed and easy writing Transparent barrel, Airplane-safe - automatic pressure equalization prevents pen from leaking on board aircraft Cap, tip and end plug in writing colour, Smooth writing performance. Light colour comes with light ink for better differentiation of colours. Take your writing to new heights with Staedtler Colored Pens. Designed for aircraft safety, the pens feature automatic pressure equalization to prevent leaks while on board. You'll love the ergonomic triangular shape that promotes comfort and ease, and the transparent barrel that lets you see the ink level. Not to mention, the smooth writing performance, and light color options with light ink, making it easy to differentiate between colors.