{TAIL ~ A gap} is defined between {HEAD ~ each lobe}, the gap being defined at the radial outer edge 
{ TAIL ~ A gap } is defined between { HEAD ~ each lobe } , the gap being defined at the radial outer edge
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH