The SIG Sauer P320 M18 Slide Assembly is a factory‑built, optics‑ready M18 slide finished in coyote PVD and fitted with SIG’s ROMEO‑M17 reflex sight and SIGLITE sights — a turnkey way to convert or refresh a compatible P320 fire‑control unit into an M18 configuration. Built from stainless steel and listed at 12.4 oz, this 3.9″ 9mm slide assembly includes the loaded‑chamber indicator and the factory‑mounted ROMEO‑M17 for out‑of‑the‑box sighting performance, making it ideal for users who want a military‑style M18 appearance and a pre‑installed optic without having to mill or fit parts themselves. Note: verify the retailer listing for whether the barrel and recoil components are included with the assembly before purchasing — some listings sell the slide assembly alone.