noun, noun which may take the genitive case particle 'no'
AAA size (battery)
Refers specifically to the AAA battery size, commonly used in small electronic devices. Often used attributively with の.
このリモコンは単４型の電池を使います。
This remote control uses AAA batteries.
単４型の乾電池を買ってきてください。
Please buy some AAA dry-cell batteries.
Compound of 単 (single, unit) + ４ (four) + 型 (type, model), referring to the fourth standard single-cell battery size in the Japanese classification system.