Buy both the medium & small waterbrushes & save 1 on the individual prices. The handy water holder & brush all in one.A Derwent Waterbrush is perfect for taking out into the field; no need for water pots & endless traditional brushes! They are portable, easy to use & great alongside any of our water-soluble pencils & sticks. They house water in the barrel of the brush which is supplied to the fibre tip via a valve, giving a constant flow of water when the brush meets paper. For wet on wet techniques just add slight pressure to the barrel & to clean it simply apply pressure to the barrel & the dirty water will work its way out of the brush. The Waterbrushes have a patented valve that stops water from leaking & potentially ruining artwork. The medium Waterbrush with its larger brush head is perfect for broader strokes. The small Waterbrush is the ideal choice when you want to do intricate painterly detail, as the brush head is extremely fine.