Premium grade optical glass filter; high quality, single threaded, ultra slim multi-coated ND4 filter Premium grade anodized aluminum ring; 145mm x 1mm standard filter thread; filter ring is 3mm thick, half the size of a standard filter ring Enables slow shutter speeds to be used, allowing film to record movement in subjects such as waterfalls, clouds, or cars. Decrease depth of field by allowing wider apertures to be used, in turn helping to separate subjects from their background Decrease the effective ISO of high-speed film and allow it to be used outdoors in bright situations. Allows video cameras (which have fixed shutter speeds) to film subjects such as snow, sand or other bright scenes that can cause overexposure