The region includes {HEAD ~ an acetal material portion} having {TAIL ~ a thickness} less than the certain overall thickness 
having
The region includes { HEAD ~ an acetal material portion } having { TAIL ~ a thickness } less than the certain overall thickness
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH