Crankshaft bearings for Let's, sizes 6204 and 6000 (manufacturer TATA). They secure the crankshaft in the crankcase and let it rotate while the engine runs.
Replace them if the engine hums and vibrates. The job requires splitting the crankcase; during the repair, replace both bearings together with the oil seals. After installation, check that the shaft rotates without binding and without noticeable play.
