A linear ball bearing unit 1, wherein {HEAD ~ said retaining side covers} are made of {TAIL ~ a sintered metal} 
are made of
A linear ball bearing unit 1 , wherein { HEAD ~ said retaining side covers } are made of { TAIL ~ a sintered metal }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL