DetailsIf you have back/shoulder pain, chronic pain or muscle pain, try this 4 channel TENS unit muscle stimulator and customize your exclusive massage. Offer 4 programs, 48 massage modes, 20 intensity levels, 6 timer settings and 8 electrode pads. Built in a 300mAh rechargeable battery for up to 7 hours of continuous massage. Feature clear screen and screen lock, easy to read and operate. Smaller than a mobile phone, portable and easy to carry for for on-the-go use. Relax with this electronic p