APK Identification 50mm Circular electrodes are round, single-use solid gel electrodes for accurate monitoring of heart signals. Each electrode has an Ag/AgCl (silver/silver chloride) sensor on a conductive ABS plastic stud, a solid conductive gel, a skin-friendly adhesive and a foam or non-woven cloth backing. The Ag/AgCl sensor minimizes signal noise and impedance, and the solid gel acts as the interface between the skin and the sensor, translating the heart's ionic electrical signals into an electron flow for an external device such as an ECG machine or monitor. The 50mm Circular shape gives a large contact area with the skin for a steady signal and good adhesion. Manufactured under an ISO 13485:2016 certified quality system.