Biopac Systems Inc. EL507 EDA (Isotonic Gel) Electrode - Sealed Pack of 100 This was unused surplus from a college. At the time of this listing, I have several of these. They have a date on them of 01-2012. These dry electrodes are designed for electrodermal activity (EDA) measurements?application of GEL101A isotonic gel (available separately) is required for EDA measurements to establish physiological ionic equivalency to the skin surface. These dry electrodes incorporate a gel cavity situated between electrode and skin surfaces that helps to stabilize measurements and reduce motion artifact. The electrodes conform and adhere well to a variety of skin surfaces. Typically applied around fingers to create a firm bond, these electrodes are also very suitable for attachment to the palm, wrist, toes or sole. Standard snap connection Ag/AgCl contact Incorporates gel cavity (16 mm diameter, 1.5 mm deep) Strong adhesion Size: 27 mm wide x 36 mm long x 1.5 mm thick contact: 11 mm dia Use with isotonic gel (GEL101A) and unshielded lead (LEAD110A clip lead, SS57LA EDA lead set, BN-EDA-LEAD2 or BN-EDA25-LEAD2). C6-8 fdk 80211258