a metallic sleeve arranged over {HEAD ~ the magnets}, wherein gaps are formed between the magnets and the metallic sleeve, and {TAIL ~ the shell} is arranged over the metallic sleeve 
a metallic sleeve arranged over { HEAD ~ the magnets } , wherein gaps are formed between the magnets and the metallic sleeve , and { TAIL ~ the shell } is arranged over the metallic sleeve
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD 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