TENS (transcutaneous electrical nerve stimulation) unit's are devices that send small electrical currents to targeted areas of your body. These currents send electric pulses through your skin. They control abnormally excited nerves and also release endorphins. When the current is delivered to the targeted area, the electricity stimulates the nerves and send signals to your brain that block, or scramble, normal pain signals. TENS machines are used in a wide variety of pain treatment and can be extremely beneficial in many different situations. All orders over $99 receive FREE Shipping. If you have any questions please feel free to contact us toll free at 877-977-7709, we are open Mon-Fri 9-5 EST.