The FL-dies are used to size the cartridge case on full length.
In addition to a removable expander the FL-dies have an integrated primer ejector pin. All used spindles, the expander and ejector pin can be replaced easily if necessary, with just little effort.
 
Especially the dies with 1 ¼"-12 Gg thread are characterized by highest steadiness and durability. The required forces for the sizing process are significantly smaller than with the 7/8”-dies.
This protects your reloading press and gives more even results, than the sizing with too weak reloading tools.