A shackle device which couples {HEAD ~ the first and second pistons} to one another, allows a relative axial displacement of predetermined magnitude between {TAIL ~ the first and second pistons} 
A shackle device which couples { HEAD ~ the first and second pistons } to one another , allows a relative axial displacement of predetermined magnitude between { TAIL ~ the first and second pistons }
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL