From the manufacturer:
Our new Waterbrush V2 set comes in three convenient tip sizes for a variety of creative strokes and is perfect for water soluble paints, watercolors, pencils and inks. The durable nylon brush head keeps a sharp point and the water tight handle holds a generous amount of water. Perfect for creating on the go! Packed in a reusable carry pouch.
Three Pack includes: Fine(3mm), Medium(5mm) and Flat(8mm)
Large Flat is 12mm