... normal circumstances, after assembly without lubrication BK bearings for the shaft neck without end bearing, end closure sealing effect, and ... NTN needle bearingMain structure frame:NK- needle bearing without inner ring, light seriesNKI- needle bearing, light seriesNKS ... seriesNKIS- needle bearing, heavy seriesRNA48, RNA49- needle bearing without inner ring, size series 48 49NA48, NA49- needle bearing ...