Pitt Artist from Faber-Castell are very good pens for so-called mixed medium. This means that when you want to combine different mediums (different forms of pencils or paint) in, for example, sketches. Good for both professional and hobby artists. The pens' ink is very light-resistant and permanent on porous material (e.g. paper, not plastic). With these you can both write beautifully and color, for example in your Bullet Journal. Does not bleed through on paper (of course also depends on the paper and technique). Good in a Bullet Journal if you want to combine fineliners with brush pens, but also for garden sketches, fashion & design sketches, drawings, illustrations and brush lettering. Simply very good pencils when you want to combine different forms of techniques, but not as watercolor because they are waterproof.