Bio-Protech Adult Monitoring EKG Electrode (T815-50). Perfect for Adult Stress and Holter, General Monitoring. 55mm Round Shape, Cloth, Solid Gel. It uses an Ag/AgCl sensing element and Hydro-gel for adhesion. These are excellent components for sensitive monitoring. Hydro-gel's main advantage is one of minimizing movement artifacts by increasing the bond between the skin and the sensing element. 50/PCH, 20PCH/CS (1,000). Price per Case.