In a preferred embodiment, {TAIL ~ the passageways} are {HEAD ~ holes} having substantially equal dimensions 
In a preferred embodiment , { TAIL ~ the passageways } are { HEAD ~ holes } having substantially equal dimensions
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH