They are VERY good markers!!!
They write very well on anything (personally, I have painted with them on a case, tablet, canvas, and graffiti on a wall). Be careful when using them on paper, consider the type of paper you will be drawing on. For example, do not use these markers on regular thin paper, the thinnest paper you can use is watercolor paper if you don't want it to tear or wrinkle. (I remind you that these markers are water-based).
Every time you use it, don't forget to shake it well because otherwise it won't work.
Personally, I have never had any problems with them and I have about 30 colors. Anyone who wants can check out my YouTube channel with artwork, my name is: DRAWX art