This Styrofoam board is used to bounce light. It's reflectance qualities are more diffused than foam-core, yielding a softer less detailed soft light source.
Bead Board 4×4
MPR Says: "Awesome Reflector"
"Highly useful Styrofoam sheets with one side white, one side silver. Great surface to bounce light off of for a soft reflection or harder source with the silver side. Hang it in the perfect position using a c-stand and a platypus. Comes in 4x4 and 4x8 sizes. Great tool to have in your grip kit or on your grip truck."