a nonmetallic cover overlying {HEAD ~ at least the outer surface} of {TAIL ~ the outer flange}; and 
of
a nonmetallic cover overlying { HEAD ~ at least the outer surface } of { TAIL ~ the outer flange } ; and
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH