This style of battery is known as the nunchuck type (often referred to as 'crane-type' as well), for obvious reasons. Manufactured by Intellect for Swiss Arms, the quality of this battery is superb - it is long lasting both in terms of individual use and overall lifespan. Of course it is critical to use only high quality smart chargers to get the most out of the battery; inferior chargers risk the battery burning out, drastically reducing its lifespan. Designed primarily for crane-stocks and front wired M4 Carbines with full outer barrels, this battery will also fit in full-stocked guns e.g. AK47 series, M16 etc.