Individuals with neurological impairment, particularly those with cervical level spinal cord injuries (SCI), often have difficulty with daily tasks due to triceps weakness or total loss of function. More demanding tasks, such as sit-skiing, may be rendered impossible due to their extreme strength demands. Design of exoskeletons that address this issue by providing supplemental strength in arm extension is an active field of research but commercial devices are not yet available for use. Most current designs employ electric motors that necessitate the addition of bulky power sources and extraneous wiring, rendering the devices impractical in daily life. The possibility of powering an upper extremity exoskeleton passively has been explored, but to date, none have delivered sufficient function or strength to provide useful assistance for sit-skiing. We seek to rectify this with the design of a passively actuated exoskeletal arm brace capable of operating in two, adjustable-strength modes: one for low level gravity compensation to aid in active range of motion, and the other for more stringent weight bearing activities. The mechanism developed through this paper allows for an affordable, lightweight, modular device that can be adjusted and customized for the needs of each individual patient.