The pens are popular for use in Bullet Journals to highlight lists, among other things. They are also fun to use for various forms of decorations! Other popular areas of use are to mark in stitch descriptions or as a bingo pen. Simply pens with lots of uses!
There are different models of these pens. It is available as a single variant but also with double tips where the second tip is a thinner fiber tip. In this model, it is available as pieces, in packages and metallic.