This replacement Li-Ion battery provide a backup power source. Rated at 1000 mAh, it gives you the opportunity to increase talk and standby time. Actual talk and standby time vary depending on personal usage and system transition of your service provider. Back door is included with the battery. To reach maximum capacity and ensure longetivity of your new battery, you need to charge-discharge it for 3 complete cycles. Ideally, each charge cycle should be more than 10 hours.