One lower packing ring set around the valve stem has {HEAD ~ PTFE washers} sandwiched between {TAIL ~ flexible graphite rings} to provide fire safety and low friction 
sandwiched between
One lower packing ring set around the valve stem has { HEAD ~ PTFE washers } sandwiched between { TAIL ~ flexible graphite rings } to provide fire safety and low friction
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH