For example, in the Souverän series, the M300 is the smallest while the M1000 is the largest (slightly larger than a Mont Blanc 149).  The M600 pictured here, is a reliable work horse: well balanced with excellent ink capacity and a measured flow making it an extremely functional writing instrument. Pictured below, the M400 has all the qualities of the M600 but a little smaller with only slightly less ink capacity.  The M300 is smaller yet but with the same simple conservative style and excellent function.  People also like the M300 for its portability and usefulness in the flap of a daytimer.  It is an accurate scaling down of the full sized models.  The M800 is a full sized pen, comparable to the large pens offered by Waterman and Parker.  The M1000 is as big as they come.  It is a real handful for those who like a truly big pen.