AAA battery thickness gauges

AAA

— replacement batteries (may also be available as rechargeable batteries) are known as "mini finger" or "little" batteries. They have a cylindrical shape with a diameter of 11 mm and a length of 44 mm, usually used in 2 or 3.

The advantage of all replaceable batteries (compared to built-in batteries) is the ability to quickly replace a dead battery with a fresh one. On the other hand, such power supplies need to be bought separately — and either regularly spend money on disposable batteries, or fork out for a battery with a charger.