In accordance with yet another preferred embodiment, the first central area has {HEAD ~ a diameter} which varies between about 1.8 to {TAIL ~ 3.7 mm}, and the second central area has a diameter which varies between about 1.4 to 2.9 mm 
varies between about to
In accordance with yet another preferred embodiment , the first central area has { HEAD ~ a diameter } which varies between about 1.8 to { TAIL ~ 3.7 mm } , and the second central area has a diameter which varies between about 1.4 to 2.9 mm
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL REL OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH