The Redding Neck Sizing Dies size only the necks of your bottleneck cases to prolong brass like and improve accuracy. It is important that fired cases should never be interchanged between rifles since the neck sizing dies do not size the shoulder or body. Ideal for cartridges used in Bolt Action rifles. All dies are made using the finest alloy steels obtainable and machined on Hardinge Super-Precision lathes capable of holding the tightest tolerances in the industry. Heat treated in atmospherically controlled furnaces and hand polished for smooth, flawless functioning, these dies will maintain tolerances and last a lifetime. Inspected and ultrasonically cleaned before packaging.