This is a high-performance replacement cellular battery for the Apple MD644LL/A, guaranteed to meet or exceed the OEM specifications of your original. The cellular battery is 3.55 x 1.23 x 0.146 inches with an output of 3.6 volts. The chemistry is LI-POL at 1440mAH capacity. Manufactured by Empire Scientific, model number BLP-1277-1.4. 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.