The Holosun IRIS-RD4 is a compact, advanced quad-function aiming and illumination system engineered to meet the demands of modern professionals and enthusiasts alike. Precision-machined from 7075-T6 aluminum, the redesigned housing is 43% lighter, 29% lower, and 28% narrower than the legacy LS420, offering superior ergonomics without compromising structural integrity ideal for integration on PDWs, SBRs, and standard rifle platforms. At its core, the IRIS-RD4 combines a co-aligned visible red laser, infrared (IR) aiming laser, 60mW VCSEL-based IR illuminator, and a high-output white light delivering 1,000 lumens and 25,000 candela. This integration allows operators to transition seamlessly between daylight aiming, night vision engagements, and high-intensity white light use. The co-alignment of the lasers simplifies zeroing users can calibrate both IR and VIS lasers simultaneously using the visible laser in daylight conditions, ensuring consistent point-of-aim across environments. A key feature of the IRIS-RD4 is its top-mounted IR beam divergence slider, which enables on-the-fly adjustment of the IR illuminator’s beam pattern from wide flood to tight spot optimized for performance across a range of shooting needs. Dual independent fire buttons offer tactile, ambidextrous control of laser and light functions, while the updated rear-positioned power and mode selector provides streamlined controls. The included three-button remote switch connects via a Crane plug and offers a visible laser override function for rapid activation. For versatile power options, the IRIS-RD4 supports both the included USB-C rechargeable 18650 battery and dual CR123A batteries providing dependable power in any operational setting.