Firing Pin, BCG

The firing pin for 9mm/38/40 caliber pistols is specifically sized (0.069 diameter) to help reduce the chance of primier flow, and it provides the proper weight for reliable ignition with heavy-duty springs.  However, it may be too large to fit an STI slide.  The part is machined to exact tolerances from stainless steel, then heat treated and coated for extended service.