According to our current understanding of elementary particles, quarks are considered to be point-like particles with no size or internal structure. However, determining the precise shape of a quark is a complex task because it involves studying their interactions and properties at extremely small scales.
Quarks are elementary particles that are governed by the laws of quantum mechanics. They are always confined within composite particles, such as protons and neutrons, due to a phenomenon known as color confinement. Because quarks are always bound within these larger particles, it is difficult to directly measure their shape or determine if they are perfectly round.
Experimental evidence and theoretical calculations suggest that quarks have no measurable size or shape. However, it is important to note that our understanding of the fundamental nature of particles is continuously evolving as new experiments and theories emerge. So, while quarks are currently believed to be point-like and devoid of internal structure, future discoveries may shed more light on their properties.