US Blanks and Common Surf Foam are PU blanks (polyurethane foam)It has been the standard surfboard core for over 50 years. PU blanks can be glassed with either polyester resin or epoxy resin (epoxy becoming more popular due to its superior strength).EPS stands for Expanded Polystyrene. EPS foam is lighter and stronger than Polyurethane foam blanks. It consists of small beads of polystyrene expanded with steam and fused together under high pressures. Greenlight's EPS blanks are engineered with a special bead formula for the optimal strength, flex, and shape-ability of the blank. There is a growing demand for EPS surfboards in the world due to its superior strength to weight ratio. Greenlight is a huge proponent of EPS surfboards and has been developing, manufacturing and selling EPS blanks for over 10 years. NOTE: EPS foam must be glassed with EPOXY resin! Polyester resin will melt the foam!