This battery has nearly the same size as a AA battery (It is slightly longer), but can only be used in equipment designed for LiIon batteries, due to the much higher voltage.

Specifications:

• 750mAh IC PROTECTED Rechargeable Cell (4.2V hot off charger)
• Measures only 51.1mm in height (+/-0.1mm) and 14.4mm in width
• IC protected for a) over-charge, b) over-discharge, c) short circuit, d) current overflow of 3A+
• True protrude top design, fits all flashlights
• High discharge rate 3A+
• Nominal voltage: 3.7V, charge up to 4.2V, use CC/CV charger to charge
• Reinforced steel plate bottom, highly efficient protective PCB design
• Packaged in individual box and anti-static bag