This a Pro Series standard 45 ACP firing pin .089"-.091" diameter pin. Precision CNC machined from Solid 4150 alloy steel bar stock and heat-treated. Mil spec style firing pin for 70 series style pistols. Made for most all 1911 Colt style pistols and Clones with standard 45 acp fining pin hole in slide. Black Oxide finished, Lifetime warranty.