Preferably, {TAIL ~ the opening} has a first diameter at {HEAD ~ the top surface} and a second diameter at the bottom surface, the first diameter is greater than the second diameter 
Preferably , { TAIL ~ the opening } has a first diameter at { HEAD ~ the top surface } and a second diameter at the bottom surface , the first diameter is greater than the second diameter
OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH