The SIG Sauer P320 is a modular design of semi-automatic pistol made by Sig Sauer, Inc. of Exeter, New Hampshire and SIG Sauer GMBH of Eckernförde, Germany. The SIG Sauer P320 can be chambered in 9×19mm Parabellum (referred to here as simply 9mm), .357 SIG, .40 S&W, and .45 ACP. The handguns made in 9mm, .357 SIG, and .40 S&W calibers can be easily converted among each to be the other. A change from .357 Sig to .40 S&W requires only a barrel change. The change between 9mm to .357 Sig or .40 S&W and vice versa are accomplished using a caliber exchange kit.