Penta Prism is a five-sided prism which features two important properties. Firstly, the images formed are neither inverted nor reversed while being deviated by 90 degrees. Secondly, it is a constant deflection device where all the transmitted rays are exactly deflected by 90 degrees. Any slight movement of the prisms would not adversely affect the right deflected angle. This feature makes the prisms useful in rangefinder as well as in viewfinders of single reflex cameras. The reflecting surfaces are typically enhanced aluminium-coated with a black paint overcoat for protection.

BK7 is the most common optical glass used in high-quality optical components as it is a hard glass that can withstand a variety of physical and chemical exposure. Relatively scratch and chemical resistant, it has a low bubble and inclusion content, therefore making it an ideal choice for precision lenses. It is the ideal choice for general purpose visual and NIR applications as it has excellent transmission.