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