Molotow Squeeze Pen Set/6The set contains three Molotow Squeeze pens, 1 1mm Round 1 2mm Round 1 3mm Round 1 4mm Flat 1 7mm Flat 1 10mm Flat Fill these empty pens with water and work with any watercolor, gouache.. perfect for travel watercolors. Fill empty pens with any thin fluid: inks, dyes, watercolors and create your own pen. The secret sauce to this product; the Aqua Squeeze pen has a great system to regulate flow. You can squeeze to release more fluid, but you won't end