The Fenix ARB-L18-3500U USB rechargeable lithium-ion battery has a built-in USB port and can also be charged using an external charger. It offers an extra level of protection with an anode circuit encased in a steel housing, and as the battery is fully wrapped in steel, the risk of short-circuiting due to impact or collision is drastically reduced. 

Note: This item is packaged and priced as one unit - one battery. 

Shipping Note: Lithium ion batteries cannot be shipped via expedited shipping service due to shipping carrier restrictions. Orders that include lithium ion batteries that aren't included in lights they are meant to power will be shipped via UPS or USPS ground service.