{HEAD ~ a filter pack} disposed in {TAIL ~ the combustion chamber} along an inner diameter of the outer wall 
{ HEAD ~ a filter pack } disposed in { TAIL ~ the combustion chamber } along an inner diameter of the outer wall
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH