The RSS4ULTRA is the high-capacity flagship of the RSS4 series, purpose-built for extended autonomy. A die-cast aluminum battery compartment and streamlined housing enclose a flat LED module that maximizes space efficiency without compromising light output. The oversized compartment accommodates up to 3800Wh of lithium battery capacity for multi-day backup. Like the rest of the series, it uses a three-module design (light source, battery, solar panel); four captive screws release the flip-top cover, making servicing fast and tool-light.