This easy-to-use Dual Channel Tens Unit uses Electrotherapy for safe and effective, drug-free pain relief. Perfect to use on your back, shoulders, legs and arms, it produces a stimulating, pulsating massage that helps prevent pain signals from reaching your brain. Customize your pain relief by placing 2 or 4 electrodes onto your body, and choose from 8 different therapy modes and 20 levels of adjustable intensity. Includes 2 "AAA" batteries. FDA-cleared class II Medical Device. Approx. 7"L x 6"W x 2"H.