Apple's New Battery Case for Iphone 6s and 6

Apple has introduced a battery case designed specially for its new iPhone 6s and the older iPhone 6.

Apple’s new battery case, which has a soft microfiber lining on the inside will also protect the device, and on the outside, the company had given gone for a silicone cover.
Apple says that

with the Smart Battery Case on, the intelligent battery status is displayed on the iPhone Lock screen and in Notification Center, so you know exactly how much charge you have left.