Foamcore is a lightweight very strong material made with a dense polystyrene center and covered with a thick paper on both sides. It is used as a sturdy reflector for the photo and cine industries. Even a large piece weighs little and light reflected from surface is soft and even. The Foam Core Fork stabs into the foam center and then the stud is placed in a grip arm or any other 5/8" baby receiver to be positioned anywhere as a reflector to bounce light or flag to block it.