This chapter on the materials for concentrated solar power systems focuses on optical components. It describes the general optics elements. The chapter provides details on the three types of optical surfaces that are used in solar fields: reflective, transparent and absorbing surfaces. It defines the performance indicators associated with the considered optical function, and describes the existing technologies and those being developed in order to reach these performances. Particular attention is also paid to the operating conditions specific to each type of optical surface, the material aging phenomena that these conditions may trigger, and the solutions being considered in order to limit the aging-related degradations. Transparent surfaces are present, in the form of sheets of glass (windows or tubes), in many concentrated solar technologies. Their main role is thermal insulation and/or physical protection of other elements, such as absorber components, or even sometimes reflective mirrors.