Royal Talens Ecoline Brush Pens - 5 Pen Primary Colours Set
These brush pens by Royal Talens have ink which adheres well to watercolour paper, drawing paper and cardboard. The ink is not waterproof when dry, so you can work on it more by wetting it again.
Whether you're practising calligraphy, product design, illustrations, fashion design, calligraphy or children’s drawings, the brilliant colours of this liquid water colour paint bring every piece of art to life.
Pack of 5 pens with one each of Black, Sky Blue Cyan, Magenta, Lemon Yellow and Blender. The Blender pen can also be purchased separately here
I have found these to be the easiest brush pens to use for calligraphy.