These RCBS factory replacement decapping units are the same ones we ship with our products - so you can rest assured they will work. These replacement decapping units feature an expander rod, expander ball, and decapping pin. They are used in sizing dies to de-prime the case and expand the case neck in bottleneck cartridges. It is always a good idea to keep an extra decapping unit on-hand so you can ensure your reloading sessions do not get interrupted if you ever damage them during use. Factory Replacement Part Precision Machined to ensure concentricity Expander Rod, Expander Ball and Decapping Pin .17 Caliber Limited Lifetime Warranty Compatibility .17 Remington Fireball .17 Remington .17 Hornet .17 Ackley Hornet