Formatt Hitech 100x150mm (4"x6") Neutral Density Reverse Grad 0.9 (3 Stops) for 100mm Modular holder Firecrest holder Lee 100mm System Nisi 100mm system compatible with all 100mm holder systems 3 stop (0.9) soft Edge reverse Graduated ND filter. Made in the UK in rugged and durable Cr39 resin Densest part of graduated ND is at center of filter, graduating to lightest part at top Ideal for sunrises and sunsets which require adjustment of light at horizon Compatible with Format Hitech 100mm , Fire crest 100mm, Lee 100mm and Nisi 100mm systems Firecrest filters are supplied in durable clam shell packaging