Pre-gelled, self-adhesive, & reuseable electrodes with snap button, 32 mm. For use with TENS products. Product will conduct mircro-current when attached correctly to appropriate devices. Excellent trace quality for more accurate results. Can be used in various applications of ECG/EKG tests or monitoring. Compatible with Healy devices. Each package contains 4 electrodes. Condition is New. Shipped with USPS First Class.