In a tubular shaft, the open of the shaft is also left open by the ball so that wires or {HEAD ~ other materials} may be passed through {TAIL ~ the shaft} 
passed through
In a tubular shaft , the open of the shaft is also left open by the ball so that wires or { HEAD ~ other materials } may be passed through { TAIL ~ the shaft }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL