Twenty-one rounds in a frame derived from the original P365 micro-compact platform — that's the headline of the Sig Sauer P365-Fuse. Released in June 2024, the Fuse stretches the P365 architecture to a 4.3" barrel, a 21+1 magazine, and a Picatinny-railed full-size LXG grip module while keeping the slimmer P365-family slide width. At 23.1 oz, it carries lighter than most service pistols despite holding more rounds.

The Fuse uses the same modular trigger group as the rest of the P365 line, which means owners can move the chassis between grip modules and accessory configurations. Compared to the Sig P365 X-Macro, the Fuse adds 4 rounds of capacity and a longer slide-and-barrel package while retaining the same slim grip profile. Compared to the Springfield Hellcat Pro OSP, the Fuse offers 6 more rounds in flush-fit configuration for a similar overall length and weight class. The Romeo-X optic footprint cut, factory fiber-optic front, and ambidextrous controls are all standard.

The compromise is that the Fuse stretches an originally compact platform to its outer limits — the long grip exposes more of the pistol when concealed, and the magazine spring tension on a 21-round flush stack is notable. The real selling point isn't compactness or innovation; it's the magnitude — a flush-fit 21-round 9mm in a frame that still rides closer to a P365 X-Macro than a Glock 17.