Mophie, as this brand makes some of the most popular battery cases out there, which often look and behave better than the official manufacturer ones.
That's because Mophie has been in this business for a good amount of time now, and, while its products come later in a phone's lifecycle than, say, the Chinese counterparts, the battery cases are usually done very carefully, and offer the most band for the buck in terms of safety, capacity and ergonomics.
Mophie makes power banks of various capacities, too, and they come with integrated cables for added convenience, letting you charge your iPhone or Android device on the go in a more compact form. Those slim and convenient creations are now on sale, today only, at the whopping 35% off, so if you are in the market for a good external battery to back up your device's juicer on the go, hit the source link below.
You can, for instance, get the compact 12,000 mAh Mophie Powerstation Plus XL you see here on the right for $64.95 (down from $99.95). It comes with a switch-tip charging cable that charges both Apple and micro USB devices with a fast 2A output, or you can attach your own cable to the second USB port to charge one more device of your choice simultaneously