{TAIL ~ The block} may have a length between {HEAD ~ about 10 μm} and about 50 μm, and a width between 10 μm and about 50 μm 
{ TAIL ~ The block } may have a length between { HEAD ~ about 10 μm } and about 50 μm , and a width between 10 μm and about 50 μm
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH