A slidable sleeve slides along {HEAD ~ the hollow body} to close {TAIL ~ the orifices}, causing the plunger to rise and carry accumulated fluid to the well surface 
A slidable sleeve slides along { HEAD ~ the hollow body } to close { TAIL ~ the orifices } , causing the plunger to rise and carry accumulated fluid to the well surface
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH