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