Hi, thanks for the question.
thats difficult to answer. so this will only be speculations. As far as I have observed using electron microscopy the size distribution seems to be narrow. If exosomes are produced in the endocytic compartment forming the multivesicular bodies and using the same invagination machinery I would guess this would produce vesicles of similar size - equivalent to the formation of clathrin coated pits and clathrin coated vesicles. but going forward in this field will for sure tell us in greater detail the mechanisms involved in the MVB formation and exosome release.