The Fenix ARB-L18-2900 is a high capacity 18650 Li-ion rechargeable with a protection circuit in the anode to help prevent short circuits, over charge/discharge and over heating. The battery also includes pressure relief vents which expel waste gas in the rare case of an internal short circuit preventing an explosion.
Fast professional and quality product.
Some confusion with proper size
It's a battery.... Works just fine as a back up. Nothing really to compare it to.
The AR-L18-2900 batteries are great lasting for a long time.