This is the FND-30C02-40, a 30 mm diameter, unmounted Neutral Density Filter from OptoSigma. The filter is made of N-BK7 Schott, a high-quality borosilicate glass known for its excellent optical properties. The N-BK7 Schott material ensures high transmission and low absorption across a wide spectrum, making it ideal for various applications in the visible light range, specifically from 400 to 700nm.
The filter features a thickness of 2mm, providing robustness and stability. It is coated on both the front and back with Opt FND-40, a reflective neutral density coating. This coating reduces the amount of light transmitted without altering its color, providing a uniform attenuation of the light across the entire spectrum.
The FND-30C02-40 is in stock and available for immediate purchase through the provided weblink. Its thin lens shape allows for easy integration into various optical systems, making it a versatile choice for a wide range of applications.