If the products features small size with detailed patterns on it, it's better to choose the soft silicone like 5-15 Shore A, because it is more easy to de-mould and not damage the pattern of mother mold.
If the products size is medium and with detailed patterns, it is better to use medium hardness silicone rubber, like 20~25 Shore A with better mechanical properties and long duration time.
For large size of product molding, such as products with size more than 50cm will need harder silicone with 30~40 shore A. High hardness silicone could be more stable in shape and form when molding for large size of products.
If non-shrinkage molding is required, we would like to recommend our platinum cure silicone. Platinum cure silicone is suitable for prototyping and also widely used in artificial stone molding.