The four monolithic objects have been estimated to have mean diameters in the range 30-120 meters and periods in the range 2-20 minutes. Asteroids of these sizes are expected to have lifetimes against catastrophic disruption of 10^{7} to 10^{8} years (Farinella *et al.*1998). Therefore, the four objects are likely nonprimordial collisional fragments of larger asteroids. Their sizes give a rough estimate of the size distribution of monolithic subunits in larger, rubble-pile asteroids; they extend up to sizes exceeding 100 meters.

Fragments from catastrophic asteroid disruptions are expected to be in excited, non-principal axis rotation states (Asphaug and Scheeres 1999). The fact that we have found no indication of a tumbling due to a non-uniform rotation in any of the four monolithic asteroids is not surprising, however, since their dumping timescales are estimated to be in a range from 10^{3} to 10^{7} years (Harris 1994), thus likely shorter than their ages.

In Fig. 7, the distribution of spin rate vs. diameter is plotted for 753 asteroids of all sizes (30 m to 1000 km), including the three objects from this paper. (See Pravec and Harris 1999 for a description of the data sample.) The monoliths form a distinct group in the upper left corner. A possible tendency for an increase of the spin rate with decreasing size in this range, though predicted from the theory (Harris 1979), has to be confirmed by further observations.