Pens that come with their own outlines.
Most of these work on the dual brush system: that means if you change the size of the bottom brush, you need to change the size of the top. You'll have to do the same with the angle or any other setting you change too.


The hollow Squares:


I had multiple square tips, so you get a range of soft to hard square brushes. Fun for a glow effect. :0

These are classic outline brushes, but with squares. Please adjust the size pressure curve, speed, & angle to your liking.

These are classic round outline brushes, with an extra outline on top. Fun for details like shoelaces & writing. The last brush is a double brush that plays with the brush blending mode - feel free to delete it if you don't use it.
Square
Round