"Two high-quality Tens electrode lead wires. These durable lead wires each use the 2.5mm mini-plug to two 2mm pin connectors. Note: Make sure that your device uses the 2.5mm mini-plug (smaller than a headphone size plug). If your device has the standard 3.5mm port (headphone jack size), we offer these on Amazon as well. Used for electrode pads that accept the industry standard 2mm pin connector."