{HEAD ~ The piston head} is fitted into {TAIL ~ a cylinder} which divides the cylinder into two hydraulic or pneumatic cells 
is fitted into
{ HEAD ~ The piston head } is fitted into { TAIL ~ a cylinder } which divides the cylinder into two hydraulic or pneumatic cells
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH