Multi-Resistant Coating (MRC) with Nano Technology The nano coating is an outer layer of protection that comes standard with all XS-Pro Digital MRC filters. The nanotechnology based characteristic (lotus effect) produces a better beading effect with water making the cleaning of this filter even simpler and faster than ever before. MRC nano has an improved outer (8th) layer over regular MRC. MRC by B+W is not only an extraordinarily effective multiple layer coating, it is also harder than glass, so that it protects filters from scratches (for instance when cleaning the filters), and it is also water and dirt repellent, thus facilitating filter maintenance.