At least one, and preferably both of the aforesaid half shells are closed by {HEAD ~ associated sealing sheets} the connection of which on the facing surfaces leads to the connection of {TAIL ~ the two half shells} 
At least one , and preferably both of the aforesaid half shells are closed by { HEAD ~ associated sealing sheets } the connection of which on the facing surfaces leads to the connection of { TAIL ~ the two half shells }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH 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 TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL