It is preferred that at least about 60%, at least about 70%, at least about 80%, {TAIL ~ at least about 90%}, at least about 95%, and ideally about 100% of the particles are of {HEAD ~ the same size} 
It is preferred that at least about 60 % , at least about 70 % , at least about 80 % , { TAIL ~ at least about 90 % } , at least about 95 % , and ideally about 100 % of the particles are of { HEAD ~ the same size }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD