The AA battery (or double-A battery) is a standard size single cell cylindrical dry battery. The IEC 60086 system calls the size R6, and ANSI C18 calls it 15. It is named UM-3 by JIS of Japan. Historically, it is known as D14 (hearing aid battery), U12 — later U7 (standard cell) or HP7 (for zinc chloride 'high power' version) in official documentation in the United Kingdom, or a pen cell.