Needle roller bearings are fitted with fine long rollers (roller diameter d ≤ 5mm,LD ≥ 2.5,L for roller lengths), radial structure compact, its diameter size and load capacity is the same as with other types of bearing, outer diameter minimum, especially suitable for radial mounting dimensions restricted support results. According to using occasions different, can selection no within ring of bearing or roll needle and maintained frame component, at this point and bearing match of axis neck surface and shell hole surface directly as bearing of within, and outside scroll surface, for guarantee load capacity and running performance and has rings bearing same, axis or shell hole roll road surface of hardness, processing precision and surface quality should and bearing rings of roll road similar. Such bearings can only accommodate radial loads.