The Sig Sauer Romeo-RS is Sig's enclosed-emitter pistol red dot - a closed window keeps debris, weather, and contact damage out of the optical path. Compact footprint matches the Shield RMSc cut, so it fits the Sig P365 family, Glock 43X / 48, S&W Shield Plus, and other slim subcompacts. 3 MOA dot for precision-friendly carry use. Specs: Reticle: 3 MOA red dot Housing: aluminum, matte black, fully sealed enclosed emitter Illumination: multi-step brightness, motion-activated Battery: top-loading (no remount to change) Footprint: Compact / Shield RMSc - fits Sig P365 / Glock 43X-48 / S&W Shield Plus cuts Waterproof and shock-resistant Compact vs Pro footprint: The Compact footprint is the smaller two-screw RMSc-style mount, used on slim subcompact pistols. The Romeo-RS Pro footprint (sold separately) is wider and fits larger duty/full-size pistols.