In addition, the internal surface of the cylinder and {HEAD ~ the external surface} of {TAIL ~ the piston} are grooved or keyed so as to prevent rotation of the piston inside the cylinder  
of
In addition , the internal surface of the cylinder and { HEAD ~ the external surface } of { TAIL ~ the piston } are grooved or keyed so as to prevent rotation of the piston inside the cylinder
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH