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