Use AAA battery (not included), safe and powerful pulse massager. When you open this TENS unit, it will send electrical current via the leads to the pads on your skin to help ease body pain, like back, hand, knee, leg, shoulder, neck and elbow pain, or other less common use like period pains and sports lnjuries; improve sport injures, arthritis and sciatica; stimulate muscle, enhances blood circulation, ease tiredness, enhances immunity, improve sleep qualityThey are dual channel pulse massagers, you just use it about 15-20 minutes per session, not only do you get the benefits of pain relief, you can stimulate your muscles and improve your fitness as well, most commonly used for musculoskeletal painThere are 12 massage modes and 4 pads for reliefing body stress and pain, to be healthier and energetic. Small, safe pulse travels through two sets of electrode pads placed on your skin simultaneously. Suitable for pain relief and massage without drugs and side effectsYou can adjust the intensity and time, there are 40 level of intensity allows you to fine-tune the pulse width and pulse rate which optimize sensitive control to relax your particular pain; A pre-programmed timer can set a predetermined duration from 10 up to 60 minsIt is very compact and portability, pocket-sized and dual-output design enable you to massage more body parts anywhere, great for home and office. The digital LCD backlit feature makes the screen clear and easy to read