The materials that can be cast in a silicone rubber mold are two-part polyurethane or a silicone rubber. Typically urethane is used due to the availability of a wide range of material properties. Material Properties used to select the Urethane Casting Material to be used:

• Hardness from 10 shore A to 80 shore D
• Rigidity
• Impact Strength
• Heat Deflection temperature
• UL Rating
• FDA Approved
• Color desired (some urethanes has a base color which affects using it to make white or light colored parts). Clear materials can also be specified.