A width Pb of the bottom portion of {HEAD ~ each protrusion} formed between {TAIL ~ the striations} and a width Wb of the lower base satisfy Pb<Wb 
formed between
A width Pb of the bottom portion of { HEAD ~ each protrusion } formed between { TAIL ~ the striations } and a width Wb of the lower base satisfy Pb < Wb
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH