These 50 round blocks are machined from ¾" material and are anexcellent choice for short to medium length cases. See chart for thecorrect size. Note: The #PB09 block only has 32 holes due to thecase head size. “S” blocks have shallower holes for short cases.
Big Book Catalog, Issue:68, Page:537
Sinclair, Issue:5B, Page:080