As mentioned above, the distance between {HEAD ~ the brush members} arranged in {TAIL ~ series} can vary 
arranged in
As mentioned above , the distance between { HEAD ~ the brush members } arranged in { TAIL ~ series } can vary
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH