{HEAD ~ A first monoblock element} is formed of {TAIL ~ a preferably circular horizontal rubbing plate} including a cone frustrum at its center 
is formed of
{ HEAD ~ A first monoblock element } is formed of { TAIL ~ a preferably circular horizontal rubbing plate } including a cone frustrum at its center
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH