SL Track & Shoulder Detector: You can manually adjust the width of the shoulder to 10 positions. With 53'' long SL track, this massage chair closely fits the curve of your body to achieve a larger massage range. Zero Gravity with Space-saving Design: The backrest of massage chair has adjustable angles from 129° to 157°. The ultimate relaxation will be the 3-degree zero gravity function, positions that lift your calf to the same height as your heart and simulate a weightless state to reduce the pressure on the heart, spine and neck. The space-saving design is only 2'' from the wall. Negative Ion Generator & Blue-tooth Speaker: This massage chair can produce negative ions to strengthen your metabolism and build up a strong body. 3D digital audio design links with your smart devices and introduces soothing music and audio reading during the massage. And you can select those functions through remote control with LCD color display or the shortcut key on one side of the armrest.