Formatt Hitech 100x100mm (4"x4") Neutral Density 1.2 (4 Stops) for 100mm Modular holder Firecrest holder Lee 100mm System Nisi 100mm system compatible with all 100mm holder systems 4 stop (1.2) standard ND filter Reduces light by 4 F-stops across the whole image Made in the UK in rugged and durable CR39 resin Compatible with Formatt Hitech 100mm , Firecrest 100mm, Lee 100mm and Nisi 100mm systems Enables use os slower shutter speeds, decrease of depth of field, decreasing of effective ISO