Duracell AAAA, LR61, MN2500, LR8D425, MX2500, E96, N539-ND, E96BP-2

Alkaline batteries 

The AAAA battery is 42.5 mm long and 8.3 mm in diameter with 1.5 Nominal Voltage and 500-600mAh typical capacity.  They can be used in LED penlights, Laptop pen, glucose meters, laser pointers, headphone amplifiers and powered computer styluses. They can also be known as MN2500 or MX2500. These cells are similar to AAAA cells and can be used in their place in some devices, even though they are 3.5 millimetres (0.14 in) shorter. This size battery is also classified as R8D425 (IEC) and 25 (ANSI/NEDA).