SCHOTT NG Absorptive Neutral Density (ND) Filters feature nearly constant transmittance in the visible spectrum, attenuating light through absorption. The filters are available in 6 materials, each with a thickness of 1, 2, or 3mm. Filters can be stacked to achieve custom optical densities. SCHOTT NG Absorptive Neutral Density Filters are used in a variety of machine vision, factory automation, and analytical instrumentation applications. Please contact us for custom size or optical density requirements.