100x100mm filter reduces light by 2 stops. Fire crest technology is hyper neutral across all spectrums, including UV, visible, and infrared. Made from 2mm Schott Superwite glass, the finest optical glass available. Fits the Formatt-Hitech 100mm holder system, so a single filter is usable on multiple lenses. Made in the UK on the most advanced computer-controlled manufacturing equipment in the industry.