The nuances extreme ND64 is a solid ND filter with a full 6-stop light reduction. All nuances extreme filters are made from a new type of tempered optical glass that is 4 times stronger than the previous series. This means your new filters can travel with you into any extreme conditions and withstand those inevitable drops, nicks, and scratches that can happen to any photographer. A new coating process ensures uniform Density. This process results in stunning neutrality and absolute color consistency throughout all types and densities in the series. So switching from one Density or style to another will still yield the exact same color results, No adjustments necessary. These filters have an industry standard 2mm thick Glass and rounded corners to make them easy to insert into a filter holder. If a light-tight seal is needed, Cokin recommends using the back slot of the EVO Series filter holders.