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