Samsung BK91/SNN5758/SNN5758A Extended Battery - Non-Retail Packaging - Black Motorola batteries keep your phone powered up when you need it most. The Motorola BK91 Extended Battery is a longer lasting stronger capacity battery. Protect your phones warranty by using only Motorola Original batteries that are specially designed for your phone to deliver reliable, optimal performance. This battery requires an extended battery door specific to your phone model. Motorola Extended Battery