Relative dust grain surface of all grains below a certain radius, plotted cumulatively. In addition, the upper limits for the small- (radii of 5 nm to 106 nm) and intermediate-sized grains (radii of 50 nm to 47 μm) are plotted. The upper limit for the largest grains (radii of 22 μm to 1 mm) is identical to the right boundary of the diagram. As the average and not the maximum radius of a certain bin is drawn, there is a gap at the right boundary of the diagram. For details, see Sect. 3.1.3.