The SIG Sauer Caliber X‑Change Kit — P320 Carry .40 S&W (CALX‑320XCA‑40‑BXR3) is a factory OEM conversion kit that lets you turn a compatible P320 fire‑control unit into a .40 S&W carry‑length pistol. The kit ships as a drop‑in package with a 3.9″ slide and barrel/recoil assembly, XRAY3 day/night sights, an optics‑ready top plate, a carry‑length grip module (medium) in black, and one 10‑round steel magazine. Ideal for owners who want a factory, no‑gunsmith conversion to .40 S&W in a carry footprint, the Cal‑X kit delivers SIG fit‑and‑finish and sighting provisions out of the box — just verify your P320 FCU compatibility (and local magazine/capacity laws) before installation.