EPS stands for expanded polystyrene. The foam is very similar to your standard foam cooler that is used to keep your drinks cold during the summer. The only difference is the size of the cells or foam beads. In expanded polystyrene the cells are about 1/8th the size of your regular lunch cooler. This is the difference between polyurethane and EPS, EPS foam cells are larger, and polyurethane cells are small almost sand-sized. The other difference between poly and EPS foam is how it is glassed. Both foams can be hand shaped the same way, but when it comes to lamination EPS must be coated using epoxy, if polyurethane based resin is used the foam melts. Polyurethane foam blanks can be laminated with either epoxy or polyurethane resin.