ASP lithium-Ion rechargeable batteries are custom-fabricated to provide increased energy density and longer life. The ASP 18650 rechargeable battery is optimized for use in high-drain devices such as our performance flashlights. It also features a PCM protection circuit to guard against excessive charge/discharge cycles. IMPORTANT: This battery is designed exclusively for use in ASP tactical flashlights (and conversely, ASP Lithium-ion batteries are the only rechargeable batteries that should be used in our lights). It features a proprietary terminal design that eliminates the risk of inadvertently sending recharging power through a non-rechargeable battery, and therefore may be incompatible with non-ASP products. The 18650 includes a Link Case, to safely store, protect and transport the battery. It features an interlocking design that allows multiple Link Cases to be connected to one another for efficient organization.