Once considered as standard electrodes supplied with most TENS units in the past, these carbon rubber electrodes require the application of a conductive gel, spray or easier self-adhesive gel pads onto the conductive surface before applying to the skin. These electrodes are made of highly conductive carbon rubber that is durable, yet thin enough to be flexible and conformable to the body. The raised ridge in the center has a small hole that accepts the male lead wire pin. Current is dispersed throughout the entire electrode. They can be very economical, but inconvenient, especially when used with conductive gels since they need a tape patch or strap to secure them to the skin. Conductive properties usually diminish over time, so electrodes should be replaced every 6-12 months. Available in two sizes with pin connector. Made in USA.