Derwent This brush is both a handy water holder and brush together in an all-in-one tool that has been developed for artists to paint outdoors with ease. It is portable, leak-proof, easy to clean and refillable. It can be filled with water or ink and then used as a brush pen. Available in fine, medium and chisel tips the brush heads are marked with a number system that distinguishes the head type. The fine tip is labeled with the number one, medium tips are labeled two and chisel tips are marked with a three. The brush heads are made of synthetic nylon and will hold 10ml of water or liquid.