Dove prisms have the useful property that they completely invert an image by 180 degrees. If the prism is rotated about its axis the image will rotate at twice the rate of rotation of the prism. Dove prisms provide the most convenient and most precise method of rotating a beam and their long length and square profile make them easy to mount in a cylindrical sleeve. Because of the very limited field of view dove prisms need to be used with collimated or near-collimated beams. These prisms are offered with and without a broadband multilayer anti-reflective coating on the end faces. The hypotenuse face acts as a TIR surface and is therefore normally not coated. It is important, therefore, to keep this surface clean.