This is an edited version of the default G-Pen in Clip Studio Paint! It has a more grainy texture to it that makes it like a kind of pencil or rough inker. It's good for sketching, doodling, and even line work! I recommend using a 6x4 inch canvas size for optimal outcomes (plus a Dpi of about 300) though you're free to edit the brush to fit your tastes and use whichever canvas size you want!