Electromagnetic properties of quark-like particles are examined in a classical field model involving extended dual electromagnetic fields. These can have fractional charges and a confining potential that derives essentially completely from a short-range weaker potential. The combined potentials exhibit an asymptotically free spherical surface and contribute to the masses of the particles. The quarks are shown to have an intrinsic symmetry that describes their structures in hadrons. Multi- quark solutions are easily obtained for both stable and unstable particles. Each quark can undergo simple harmonic motion in a range of frequencies.