This is a high-performance replacement laptop battery for the Sony VGP-BPS21B, guaranteed to meet or exceed the OEM specifications of your original. The laptop battery is 8.01 x 1.85 x 0.81 inches with an output of 10.8 volts. The chemistry is LI-ION at 4400mAH capacity. Manufactured by Empire Scientific, model number LTLI-9185-4.4. 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.