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