Cross arm 10, however, is filled with metal, or it is {HEAD ~ a hollow metal section} which is preferably filled with {TAIL ~ a compound} 
is preferably filled with
Cross arm 10 , however , is filled with metal , or it is { HEAD ~ a hollow metal section } which is preferably filled with { TAIL ~ a compound }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL