{HEAD ~ The differential valve piston} comprises {TAIL ~ working surfaces} of at least two different diameters such that changes in chamber pressures effect different axial forces upon the piston 
{ HEAD ~ The differential valve piston } comprises { TAIL ~ working surfaces } of at least two different diameters such that changes in chamber pressures effect different axial forces upon the piston
HEAD 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 OTH OTH OTH