In the preferred embodiment of FIG 10, diameter D3 is less than {HEAD ~ both diameters} D1 and {TAIL ~ D2} 
In the preferred embodiment of FIG 10 , diameter D3 is less than { HEAD ~ both diameters } D1 and { TAIL ~ D2 }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH TAIL TAIL TAIL TAIL TAIL