The shape and aspect ratio of the A23 battery are similar to those of a common
AA battery. However, an A23 battery is much smaller than even an AAA battery,
measuring only 29 mm long and about 10 mm in diameter, with a typical weight
of 8 grams. An A23 battery is a dry cell-type battery mainly used in small
electronic key fob devices, such as keyless vehicle entry systems, home
security systems, and garage door openers. (description from Wikipedia)