Filter sizes for Leica M lenses

As you might expect, Leica offers its range of UV filters, which are recommended for the protection of the front element in everyday use but also to prevent damage when cleaning. It's much less worrying to clean a filter than a front element. However, I also recommend B+W (UV or Clear) filters, which, although made by the German brand Schneider-Kreuznach, tend to be slightly cheaper and yet are not considered inferior in any way.  The XS-Pro, now replaced by the 'Master', features a thin brass frame and a Nano coating to facilitate easier cleaning. More competitively priced offerings include the excellent Breakthrough Photography UV X2 range and the Firecrest series by Formatt Hitech, [affiliate links follow]: Leica UK Store Leica US Store Amazon UK (B+W) | Amazon UK (Formatt Hitech - Firecrest)  Amazon US (B+W)  | Amazon US (Formatt Hitech - Firecrest) As an Amazon Associate, I earn from qualifying purchases.   The following is a work in progress; th