FND-20C02-80 20 mm Dia. Unmounted N-BK7 Visible Reflective Neutral Density Filter; t=2mm 400-700nm

This is the FND-20C02-80, a 20 mm diameter, unmounted Neutral Density Filter from OptoSigma. It is designed for use in the visible spectrum, specifically between 400 and 700 nanometers. The filter is made from N-BK7 Schott, a high-quality borosilicate glass known for its excellent optical properties.

The filter features a reflective neutral density coating on both the front and back surfaces, denoted as 'opt fnd-80'. This coating reduces the intensity of light passing through the filter without altering its color balance, making it ideal for applications where light intensity needs to be controlled without affecting the spectral composition.

The filter has a thickness of 2 millimeters, which is considered 'thin' in optical terms. This thinness can be beneficial in certain applications where space is limited or weight needs to be minimized. The circular shape of the filter is also versatile, fitting into many different optical systems.

The filter's information page, which includes a catalog number and a link to the vendor's website, can be found on OptoSigma's website. The link is valid and indicates that the filter is currently in stock.