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