If you are loading cast bullets into any caliber case, this die will prevent swage of the projectile as well as easy proper seating.
The other dies that I find to be an absolute gem is the Lee Factory Crimp Dies which are at their best with large straight walled cases (like .45's)
Pros: These are essential for quality loading cast bullets
Cons: NONE
This review was written in the old system and had content requirements that are different than reviews written today.