The Pelikan M400 is a smaller full size pen, fourth in the Souveran line. A piston filler with 24 karat gold plating, a high-quality resin casing and a viewing window to monitor the ink level. The nibs of the Souveran M400 piston fillers are made of 14 karat/585 gold. All nibs are refined with a rhodium decor and their writing qualities are tested by hand. The M400 fountain pens are equipped with a differential piston-filling mechanism.