Crankshaft bearings for DIO 34 (manufacturer TATA). They secure the crankshaft in the crankcase and let it rotate at high rpm.
Replace them if the engine hums and vibrates, if the shaft has noticeable play, or during an engine overhaul. Replace the bearings as a set together with the oil seals, otherwise the new bearing will quickly fail. When buying, compare the markings on the old bearing: they define the size unambiguously.
