Electrotherapy lead wires connect the electrodes to the output channels of the TENS unit, hence their alternate names of TENS unit leads or TENS unit electrode wires. These e-stim lead wires deliver the electric impulses generated by the TENS unit to the skin area the electrode pads are attached to. For additional comfort and easy usage, opt for longer TENS unit wires that give you more room. Wireless electrodes are also available but they tend to be heavier and bulkier.