NiSi Square System Glass Filters are manufactured from the highest quality H-K9L optical glass. These precision 2mm thick glass filters feature a multi-layer nano coating on both sides of the filter for superior high definition image quality while resisting scratches and repelling water. Considered to be a high quality alternative to resin filters and outperforming other glass filters, Nisi Square System represent the finest option for your DSLR square filter holder system. Compatible with NiSi Square System, Lee, Cokin Z-Pro, and Formatt Hi-Tech and all other 2mm filter holders.