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