Composite particles made up of quarks are known as hadrons. These include protons and neutrons, which form the nuclei of atoms. A baryon is a three-quark combination. A meson is made up of a quark and an antiquark. Antiquarks are the antimatter equivalents of quarks, opposite in electric charge and certain other properties.
Quarks have no measurable size.
The t quark is the heaviest known elementary particle. Its mass is about 190 atomic mass units. This is almost as heavy as an entire atom of gold. The lightest quark, the u, has about 35,000 times less mass than the t. The s, c, b, and t quarks are much heavier than the u and d.