This case prep tool is deigned to work in both of Forster “Original” and “Classic” case trimmers for faster, more accurate results than prepping by hand to ensure that each case is in the best condition for reloading.
Center Tool mounts in the collet side of the case trimmer to support the case mouth so you can use the chamfer and cleaner tools. Just hold the case mouth over the Center Tool with one hand while you operate the Chamfer or Cleaner by turning the case trimmer crank.
Big Book Catalog, Issue:68, Page:529
Sinclair, Issue:5B, Page:014
Sinclair, Issue:5B, Page:048