Celtic knot concrete or plaster craft mold 1096 Plastic Craft Mold to make your own Stepping Stones Measures approximately 10 1/2 inches across and 1 3/4 inches thick. Each order comes with easy to use basic instructions Celtic knot design concrete or plaster mold. The finished Celtic knot will measure 10 1/2 inches across and 1 3/4 inches thick. All of our molds can be used with concrete, cement, plaster, soap and resin. Comes with basic instructions for creating your pieces. Our molds are made of several different blends of polyethylene plastic which allows you to use the molds over and over. Our plastic is somewhat flexible so it allows for your finished pieces to be removed from the molds easily. This is a mold to pour into to make your own stones.