This is a high-performance replacement cellular battery for the Nokia LUMIA 521, guaranteed to meet or exceed the OEM specifications of your original. The cellular battery is 2.37 x 1.51 x 0.22 inches with an output of 3.7 volts. The chemistry is Li-Ion at 1050mAH capacity. Manufactured by Empire Scientific, model number BLI-1146-1. 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.