Our absorptive neutral density filters provide broadband attenuation for the visible to near-infrared region. These filters are precision polished for demanding research or OEM applications. They are available in three sizes12.7 or 25.4 mm diameter and 50.8 mm square.The 25.4 mm dia and the 50.8 mm square filters are available individually or in a set of nine. The set consists of a selection of filters packaged in a protective hardwood case. All filters are shipped with a transmission curve.Our unique assortment of filters permits easy selection of any desired density from 0 to 8 with 0.1 OD resolution by using individual filters or a combination of no more than two filters. The total filter set range is 0 to 8 OD. Optical density (OD) is defined by the relationship:OD = -log(T) or T = 10-ODwhere T is transmission (0≤T≤1). The density of a series of filters, unlike transmission, is additive.Custom densities can therefore be obtained by stacking filters, however stacking an excessive number of filters can lead to numerous unwanted back reflections.Due to the absorptive nature of the filter glass, use with high power lasers should be avoided. Power levels less than 30 W/cm2 are advised. For attenuation of high-energy lasers, our Model 935 High-Energy Variable Attenuators are recommended.