This is a high-performance replacement laptop battery for the Toshiba Satellite M55-S139, guaranteed to meet or exceed the OEM specifications of your original. The laptop battery is 8.13 x 2.52 x 0.81 inches with an output of 14.4 volts. The chemistry is Li-Ion at 4400mAH capacity. Manufactured by Empire Scientific, model number LTLI-9045-4.4. We offer a 1 Year Warranty with purchase. See this product elsewhere at a lower price? Call or email us; we have a Price Match Guarantee.