This is a high-performance replacement cellular battery for the O'Donnell PS12-21SP, guaranteed to meet or exceed the OEM specifications of your original. The cellular battery is 5.8 x 0.8 x 3.5 inches with an output of 6 volts. The chemistry is at 2000mAH capacity. Manufactured by Empire Scientific, model number NP2-12 . 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.