The clarity and precision of the Volk 20D BIO Lens make it a gold standard. In fact, this lens may be the most recognized lens around the world because it began the tradition of double aspheric lenses for BIO. It offers excellent field of view and magnification for the 20 D Lens. And with a working distance of 50 mm, you'll have a comfortable experience manipulating the lens. In addition to serving as a first line diagnosis tool, this lens is ideal for high-level central retinal examinations.