Redding Precision Expander Mandrels are machined from high-quality tool steel which is then hardened and precision-ground to their final diameter (size marked on head). They are available in .0005" diameter increments ranging from .0005" thru .0030 below nominal bullet diameter so that neck tension can be fine-tuned to suit the handloader's preference. The Precision Expanding Die is factory-assembled with one mandrel that is .0010" below nominal bullet diameter per caliber (22-338). These other Precision Mandrel Sizes are available separately here.