Mould Resin - Jewellery. Ovals, Arrowhead, Oblong, Trapezoids, Squares and Polygons. 12 Cavity Jewellery Shapes Resin Mould. measures about 135mm x 135mm. All cavities are approximately 7mm deep. The 2 squares are approximately 20mm x 20mm. The large ovals are approximately 40mm x 30mm. The smaller ovals are approximately 20mm x 26mm. The 2 irregular polygons are approximately 25mm x 22mm. The 2 trapezoids are approximately 20mm x 26mm, the Oblong is approximately 46mm x 17mm and the Arrowhead is approximately 40mm x 28mm. Measurements are approximate as it is very difficult with the moulded shapes to be precise.