This is the new version of our popular RB3 Shower Niche Shelf - Now made with 316 Stainless Steel for improved corrosion protection (compared to 304) Fits any shower niches with an inside width of 12 inches (width BEFORE tiling). Compatible with Kerdi Board SN (12x12, 12x20, 12x28) , Wedi (12x12, 12x18, 12x26, 12x38), and Houseables Shower Niche. FYI - Finished (tiled) niche will be about 11 inches wide. Marine Grade 316 stainless steel for superior protection from corrosive cleaners and hard water 3mm thickness - Perfect fit for 1/8" grout lines 1/2″ gap behind shelf prevents soap scum buildup in corners Built in washcloth and loofah hangers Installed during tile installation (cannot be installed in a finished shower niche) NOT compatible with Redi Niche or Ez-Niches As shower remodel professionals, we designed this shelf to address the deficiencies of other shower niche shelves currently available. We decided that our shelf will only attach to the side walls of the niche so our customers are free to install a feature tile on the back of the niche without interference. This "floating" design also makes the shelf much easier to clean than conventional shelves (no soapy build up in the corners). We also decided on T304, 3mm stainless steel (instead of 4mm aluminum) so it would still be super rigid, but easier to install into standard 1/8" grout lines. We also designed this shelf to install into a very common prefab and custom shower niche width (12" inside width).