Santamedical Rechargeable Tens Unit Electronic Pulse Massager is a compact, portable, micro-computer-controlled device. It can be used on many areas of the body, including the arms, neck and shoulders, back, low back, legs, feet, joints etc. It may help to relieve pain and numbness in the following situations: Stiff neck; Muscle pains from over-exercise or stretch; Numbness from some chronic conditions; Carpal-tunnel syndrome; Relieve pain and relax muscle spasms or may prevent muscle atrophy. Recharge the internal lithium battery to keep the device powered up and ready to go for massages at any time.