Sold in a pack of 2, these Energizer A23 Batteries are often found in a wide range of security equipment including alarms, key-fobs and intruder detectors. They also have applications in the medical industry with many blood pressure monitoring devices and glucometers requiring this miniature alkaline cell These Energizer batteries are made with Zero Mercury and will directly replace any battery with the codes: 1181A, A23BP, DL21, DL23, MN-21B, MN21, V23GA. They are Alkaline in chemistry so they are for single use and cannot be recharged.