This is a set of 10 of the disposable, single use cleaning cards (DLAA1129). ?At least once a year or more frequently the dollar bill unit should be cleaned and lubricated. Any time it begins having problems accepting dollar bills or to extend the life of the unit it's a good idea to clean them. Just tear open the envelope and stick the presaturated card into the machine. Wait for it to spit the card out and insert it again, several times. Each pass cleans and lubricates the belts, pinch rollers, and optical bill path.