In a further arrangement, the combined cross sectional area is {TAIL ~ less than 20%} of {HEAD ~ the cross sectional area} of the hollow interior 
In a further arrangement , the combined cross sectional area is { TAIL ~ less than 20 % } of { HEAD ~ the cross sectional area } of the hollow interior
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH