These pre-saturated use once & dispose swipe-through head cleaning cards are designed to safely & effectively remove all dirt, magnetic oxides, oils, lotions & other contaminants from all types of concealed magnetic, photo & optic sensors on all kinds of reader mechanisms. Use on card reading scanners attached to cash registers, credit / debit verification machines & ATM / POS terminals to name a few. Use at least once per week for internal, low usage card readers & once per day for external or high usage card readers.