BMW E46 coolant fitting o-rings

16×3 mm – upper radiator hose to expansion tank (1 total)
22×3.5 mm – lower expansion hose, heater hoses (5 in total)
38×4 mm – radiator hoses, lower expansion tank fitting
8×3 mm – temp sensor, lower radiator hose (1 pc)

E46 uses 200kpa radiator cap and that’s higher than previous E30/36 and later E90 models that use 140kpa radiator caps. 140kpa radiator cap part number 17137639023.
That is most likely the reason for a radiator to blow up and you can use lower pressure radiator cap on e46 M52/54 series motors to prevent that.