The MidOpt ND400-49 is an absorptive neutral-density filter with an optical density of 4.0, meaning it transmits an average of 0.01% of visible light. Surprisingly, this amount of light passing through the filter is easily detectable by the human eye. Because the glass substrate absorbs 99.99% of the light that passes through the filter, it is not recommended that these filters be used in laser applications or immediately in front of high-wattage lamps. All MidOpt filters can also be purchased unmounted and in custom dimensions upon request from Machine Vision Direct. Technical Specifications Specifications + Useful Range Min 425 nm Useful Range Max 675 nm Adhesive Backed Yes Surface Quality (Scratch-Dig) 40-20 Substrate Material Colored Glass Filter Diameter M49 x P0.75 Product Availability + Standard Lead Time 15 Days Stock Location Built to Order Product Lifecycle Active