A piston valve and {HEAD ~ a piston} are fastened into {TAIL ~ an inner compression chamber} inside the compression cylinder 
are fastened into
A piston valve and { HEAD ~ a piston } are fastened into { TAIL ~ an inner compression chamber } inside the compression cylinder
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH