Nissan & Infiniti Simple Key Smart Key. Simple Key by Car Keys Express is a new way for consumers to easily replace modern car keys. The consumer-friendly kit includes a Smart Key, emergency key insert, and EZ Installer. The emergency key blade is not required, but can be cut at most hardware stores, car dealers, or automotive locksmiths. The EZ Installer DIY pairing dongle allows you to pair your key entirely on your own. Avoid the hassle and expense of having to go to the dealership for pairing. The EZ Installer is a single vehicle use pairing tool. Once you use it on your vehicle, it cannot be used on another.