Highly conductive, these loops come with cord locks to allow tightening to your personal preference.  Just push on the button, tighten and release. An added benefit is these can double as cockrings to allow longer, more consistent erections. The inner diameter is 3.75mm so any banana plug will fit snugly.  

Comes in 6mm (thin) or 8mm (thick) diameter. These are bipolar electrodes.  Only one loop is required, one plug goes in EACH side of this loop. In the photos 8mm is on the left and 6mm is on the right. 

Order either size or a variety pair with one of each size. 

Be sure to use water-based lubricant such as Spectragel to keep the sensations smooth and avoid hot spots. Never use any lube with silicone of any kind- it weakens and degrades the rubber.