The resulting mat has {HEAD ~ areas} which are different than {TAIL ~ the rest} of the mat 
are different than
The resulting mat has { HEAD ~ areas } which are different than { TAIL ~ the rest } of the mat
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH