This is a high-performance replacement cellular battery for the Casio BTR731, guaranteed to meet or exceed the OEM specifications of your original. The cellular battery is 1.76 x 1.5 x 0.275 inches with an output of 3.7 volts. The chemistry is Li-Ion at 1020mAH capacity. Manufactured by Empire Scientific, model number BLI-1098-1. 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.