This is a high-performance replacement cordless battery for the Plantronics 80639-01, guaranteed to meet or exceed the OEM specifications of your original. The cordless battery is 1.75 x 0.88 x 0.38 inches with an output of 2.4 volts. The chemistry is Ni-MH at 750mAH capacity. Manufactured by Empire Scientific, model number CPH-515Q3. 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.