This a Pro Series standard 9mm firing pin .064"-.068" diameter pin. Precision machined from Stainless steel alloy bar stock and heat-treated. Made for 9mm / 10mm / 38 Super and 40 S&W 1911 pistols. Is also used in higher quality 45 acp pistols with the 9mm firing pin hole machined in the slide. The smaller hole diameter helps with guarding against primer pocket cratering, which becomes more present with hotter loads and higher pressure cartridges. . Made for most all 1911 Colt style pistols and Clones.