Penta prisms derive their name from their 5-sided pentagon shape. Penta Prisms are very useful in applications requiring precise 90 degree deviation without inversion or flipping the image orientation. Light incident on the input face will exit deviated by 90 degrees independent of the angle of incidence on the input face. The monolithic structure provides better stability than the use of 2 independent mirrors. Pentaprisms are often used in Metrology applications and applications prone to vibration.