Firecrest ND 4x5.65 Neutral Density Kit of 3 Filters 1 to 3 stops compatible with all 4x5.65" matte boxes Firecrest technology is neutral across the whole spectrum, including UV, visible and infra red 4"x5.65" IRND neutral density filter kit of 3 filters reducing light by 1,2 and 3 F-stops respectively Hyper-neutral Firecrest coating is sandwiched within filter, providing protection against scratching and damage 4mm thick filter made in the UK using Schott Superwite glass, the finest optical glass available Compatible with all 4x5.65" matte boxes