By variation of the liquid as well as by alteration of the porosity of the carrier {TAIL ~ the opening pressure} of {HEAD ~ the valve} can be varied 
By variation of the liquid as well as by alteration of the porosity of the carrier { TAIL ~ the opening pressure } of { HEAD ~ the valve } can be varied
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH