20mm Metallic Glass Mosaic Tiles Aura brand sparkle from copper dust that was swirled directly into the molten glass. The tiles come in sheets of 25 temporarily FACE-MOUNTED on paper, which is easily removed by soaking in water. The faces of the tiles are flat while the backs are embossed with ridges to help glue bond more securely. The 3/4-inch size is an industry standard for glass mosaic tile, which means you can use these with many other brands in the same mosaic, including both brands of the vitreous tile we sell. These tiles cut easily with our mosaic glass cutters. Opaque colors noted with OP, semi-translucent with TR.