Serengeti is known for lens technology that includes its polarized 555 nanometer spectral-management approach.
The 555 designation refers to a wavelength near 555 nanometers, close to the peak of human visual sensitivity in bright conditions. Serengeti’s lens systems are designed to manage glare and selectively filter portions of the visible spectrum rather than simply making the view uniformly darker.
The brand also became associated with photochromic lenses, which darken in response to ultraviolet exposure. That combination made Serengeti popular among drivers and outdoor users who move between changing light conditions.
The number 555 is not a model name for the whole company, and it should not be confused with a general claim that all polarized sunglasses use the same spectral technology. It is a specific Serengeti lens reference.