Four 2mm pin (female) to 3.5mm snap (female) adapters for Tens / EMS electrode leads. You want this if you have a Tens or EMS unit that has pin style cables and you want to also use snap style electrode pads. Simply insert the 2mm pins from your leads into the ends of the adapters. Then attach the adapters to the snap on the electrodes. Note: The 2mm pin and 3.5mm snap are the most common sizes of electrode wire connectors on the market. However, you should ensure that you are ordering the correct item in the correct size.