XMark Roman Chair XM-4429. The XMark Roman Chair XM-4429 is your answer to building endurance, strengthening your lower back, increasing your abdominal strength, and improving your posture. The ergonomic design, ten levels of adjustments, and wide horseshoe base of the XM-4429 provide comfort and stability. Perform sit-ups, back hyperextensions, and side bends as well as tricep dips with the integrated tricep dip station. Sculpt, build and define your body with XMark, the mark of excellence.