Particle size distribution in a collapsing pebble cloud with solid radius R_solid = 100 km at four different times. The collision speeds are initially high enough for fragmentation to occur. Later in the collapse the particles move with subvirial speeds (see Fig. 5) and the amount of fragmentation decreases. The low collision speed in the cold collapse allow the dust to coagulate and grow to sizes of ~0.1 mm. One thing we also see in the figure is that, at the end of the collapse, a small fraction of the primordial pebbles have been subject to erosion through collisions with dust and decreased in size.