The tiles are silver slate, readily available at many tile showrooms, maybe "big box" stores. The inserts were cut to a custom size by the countertop fabricator from the same material as the countertop, because there weren't granite tiles available. Many stone showrooms also have coordinating tile. I suggest selecting a stone countertop that you love, then finding a coordinating tile. Unfortunately, engineered stone doesn't have coordinating tiles, so the countertop fabricator would have to cut tiles from 2cm or 3cm material, which will project out further from the face of the backsplash than the field tile (unless you pay extra to have the tile setter "back butter" all of the field tile -- expensive!). Here's a bathroom picture where I was able to find a coordinating stone tile to match the slabs -- "Verde Laponia" quartzite. A 3/4" "sizzle strip of green was placed around each inserted tile. Hope my answer helps you. Good luck!