The Generation II expander dies are designed to fully enclose the mandrel within the die, preventing any possibility of the mandrel being extracted. An O-ring located in the die cap permits slight movement of the mandrel, enabling it to self-center within the case neck. Each of the three Generation II dies is precision-machined from stainless steel. The 7/8-14 dies are equipped with the Sinclair stainless steel split lock ring. The large caliber expander dies are compatible exclusively with mandrels ranging from .35 Cal to .50 Cal.