This device consists of two components.
The protective cover and the spare battery.
The sleeve fits 100% to the iPhone 6 is easy to install and can be removed just as easily again. The iPhone is already very well protected. (Must be purchased separately) Nevertheless, I still rate to use a screen protector. Otherwise, the iPhone is well protected from all sides.
The spare battery gives the iPhone a more than twice as long battery life. Is housed in the rear sleeve and is charged via a microUSB cable. The charging status is indicated by 4 LEDs on the back of the sleeve. Here also the switch is to activate the auxiliary battery. Is the battery in the iPhone is running low you activate the spare battery and the iPhone will be charged. For me, the spare battery with almost 1 'additional battery charges the iPhone enough.
All connections and controls are freely accessible and easy to use. The voice quality does not suffer from the additional protective sleeve.
All in all a great device. Good workmanship, top price-performance ratio.