Small pins are for pre-1990s collet-style rods designed for small-primer cartridges, as well as for current competition-style dies/rods, X Die mandrels, PPC and .357 Sig. Large pins are designed for collet-style rods for large primer cartridges, as well as for current competition-style dies/rods, 7 TCU and 35 Whelen. Straight-styles are meant for use with .50 BMG, .416 Barrett and .460 Steyr.