The building block of mosaics since the beginning of the art was the square and next came the rectangle. Edging, outlining and detail was formed by painstaking cutting of squares into rectangles. These ceramic pieces are fantastic. The longest is 20mm and the shortest 10mm, so that you will always find one that works in your project. The mix is made up of *4mm x 10mm *6mm x 15mm *8mm x 20mm. Thickness 4mm. Not suitable for outdoors unless they are sealed on the back first.