The best durometer for your project will depend on your unique project requirements. For cast stone applications, we recommend using one of our 25-40 A rubbers. For manufactured stone applications, we recommend using one of our 30-60 A rubbers. For advanced detail formliners, we recommend using one of our 50-70 A molding rubbers. For simple formliners and stamps, we recommend using one of our 60-90 A molding rubbers. Projects that require extreme detail, such as architectural restoration, will want to use a lower durometer rubber. Projects that require a large amount of rubber to hold heavy, abrasive casting material will want a harder rubber that can withstand the weight.