Yutai are good at producing right-angle prisms.They are the most common type of prisms. It is used to re-direct a beam of light at 90 degrees from the the incident direction or used as a 180 beam retro-reflector. They are often coated with various optical coatings to form cubic beam splitters and color separation cubes used in various projection systems. By means of total internal reflection (TIR), a right-angle prism may be used as a 90° reflector or as a 180° retroreflector. Except for reflection losses from the entry and exit faces, TIR exhibits 100% reflectivity over a very broad wavelength range. The reflecting surface should be coated with protected aluminum if the incidence angle exceeds that acceptable for TIR or if the environment does not allow the reflecting surface to be kept clean, as TIR requires.