Penta prism is five-sided prisms featuring a ray deviation of 90° and a right handed image. The reflecting surfaces are aluminized for increased efficiency. Slight movement of the prism does not affect the true right angle at which light rays are reflected, making a penta prism the ideal optical tool for defining a right angle in an optical system. Penta prism is made from precision N-BK7 for use in a variety of visible light applications.