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