These moulds are made of silicone and are very flexible, which means they don't need a releasing agent and your finished piece just comes out very easily and with the use of minimal force. The moulds can be used for a variety of materials including wax, polymer clays, soap, gypsum/plaster of paris , various types of resins, etc. Primarily used for resin Size: Inner cavity is approximately 5.8 inches in diameter and 5 mm deep