Smaller subatomic particles. They are not all the same size. In fact, their size is not even well defined. By the time you get down below atomic sizes, the size becomes uncertain because of various kinds of quantum uncertainty. No one has yet shown that the particle aspect of an electron has any measurable size greater than zero, but if you look at the size of the wave packet, it is quite large, depending on how you measure it.
You also had better begin to define what you mean by a subatomic particle; it is not as simple a concept as you seem to think.
