3.7V 2600 mAh 18650-Cell High-Capacity Li-ion Rechargeable Battery
This is a rechargeable Li-ion Cell in an "18650" form factor. Made by Tenergy, this cell is rated at 3.7V and 2600 mAh. This is a "protected" type of lithium cell, with a built in PCB. Ideal for use with the Li-ion Power Pack/Charger - 2 Cell (Parallax #28986) or flashlights.