Each tile is approximately 3.5mm deep and consists of a layer of metal foil sandwiched between two layers of glass; the layer of glass on top of the gold is a few milimetres thick while the one underneath is much thinner and is there simply to protect the back of the metal foil. These tiles can be used on walls but are not recommended for floors (see our Special Bisazza gold floor tiles for a toughened version suitable for foot traffic). These tiles are UVA resistant.