A genuine Ledlenser 14500 lithium-ion rechargeable cell, 3.7 V and 750 mAh, Ledlenser article 500985. The 14500 is the same size as a standard AA battery (14 mm x 51 mm) but runs at lithium-ion voltage, so it must only be used in lights designed for a 14500 Li-Ion cell, never in a device made for 1.5 V AA batteries. Use it as a spare or replacement for compatible Ledlenser rechargeable torches, so you can swap in a charged cell and keep going. The cell has a steel housing with a PVC wrap and weighs about 21.5 g. Check your light's manual for the correct battery before buying.