The base is perforated by at least one port whose length is very much less than the mean diameter and the base, external to {TAIL ~ the box} is capped by a flexible and sealed bellows adapted to form with it a pocket of {HEAD ~ variable volume} 
The base is perforated by at least one port whose length is very much less than the mean diameter and the base , external to { TAIL ~ the box } is capped by a flexible and sealed bellows adapted to form with it a pocket of { HEAD ~ variable volume }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH 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 OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD