EPS or expanded polystyrene is the material and manufacturing process behind the blank (core) used to manufacture EPS or Epoxy Surfboards. The reference to epoxy refers to the type of resin used. Epoxy surfboards are generally lighter, stronger and more buoyant than their PU (polyurethane) counterparts. This means that you can ride an EPS board with less volume. The performance advantages include more flex and increased energy return.