The JStim 1000 Infrared Joint Hand System works by sending tiny electrical signals to the joint while combining infrared heat and compression. The JStim has 2 modes of operation: DT (daytime) and NT (nighttime). The NT mode is the main treatment mode designed as a cumulative therapy to therapeutically treat OA and RA. The DT mode was designed to combat pain immediately. It is safe to use the DT mode as little or as much as needed. FDA approved. The JStim 1000 includes a proprietary signal generating device a special electrotherapy treatment wrap (for the knee or hand) and PMT's conductive solution. The wraps are one-size fits most.