This is a pair of brushes/pens (whatever you want to call them) that draw a bit like charcoal or pastels.
These were originally intended to be kinda gritty shading pens but then while doodling I realized these are more like pastels.
The one-side smooth one can have the "smooth" side changed by altering the angle setting. Right now it is set so the bottom is the smooth side.
If you erase with this pen it will usually leave fragments behind unless you scrub at it. So in this way it's like pastels or charcoal. (if you are someone who needs something completely gone, use something else to erase)
Brushes