{HEAD ~ a printing element} having {TAIL ~ an impacting surface} at its front end and a driven surface at its rear end 
having
{ HEAD ~ a printing element } having { TAIL ~ an impacting surface } at its front end and a driven surface at its rear end
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH