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