Single slices of blue carving wax measuring approximately 36mm x 20mm  and available in 3 different thicknesses, 7.2mm, 5mm or 3.8mm.
This hard wax is perfect for achieving fine detail as you can see in the picture of cast pieces, and it also has some flexibility for thinner creations without snapping. You can also heat and melt it, but please do so outside or under ventilation!