Mold Max™ XLS II is a silicone rubber that has a very low long-term shrinkage. Mold Max™XLS II has a mix ratio:100A:10B by weight. Using a gram scale, Mold Max™ XLS II Part B Being Measured. Mix Mold Max™ XLS II for at least 3 minutes Mold Max™ XLS II has a pot life of 40 minutes. After mixing, the rubber is vacuum degassed.