Extra waterbrushes are always handy to have around. They are so easy to use, just fill them up with water and you can paint for hours. They are a great tool to use with watercolor crayons or paints. These Sakura Koi Waterbrushes are available in small, medium, and large brush sizes.
I found these at Hobby Lobby, and being a lover of brush pens, snapped up a
couple of different sizes. I loaded them with fountain pen ink for use as brush
pens, but unfortunately, I found them far inferior to the Niji/Kuretake water
brushes, or to the Pentel Pocket brush pen if a brush pen is what you want. The
bristles originally had a sort of oily texture, and they just didn't have the
proper snap and spring; when pressure against the paper bent the bristles, they
would tend to hold the bend and not spring back gracefully, so the tip would
drag around rather than floating in and out like a better-quality brush. It's
hard to describe, but was very noticeable. The cap does fit well, and the
compact size would be good for portability, but again, for a waterbrush, I
recommend Kuretake instead.