Get the oem one from ford, I've had that on my 2010 since new, don't buy the knock offs, Ive had them on other vehicles and they strip or the key gets stuck, etc, unless you just need something to hold you over for a bit.
Why bother? The tweaker that tried to steal my gas cut the filler hose above the tank. He was caught in the middle of it by the security at my work and we couldn't figure out what he had been doing. I only figured it out when I went to fill it up and gas started spilling all over the place. Thankfully I had enough gas to get home and get it to the dealer once the parts arrived. It was around $650 to replace and covered by insurance.
First pic is installed on my '17. Second pic is the back-side. When unlocked, the metal tab is at 6 O'clock, then locked at 9 O'clock. Last pic is the fuel filler inlet, you can see the small opening at about 9 O'clock that the tab fits into. Would this prevent anyone from tampering? No, it's not particularly robust, and you could probably pop it off w/a screwdriver. But if someone is in a hurry and just wants to be done w/a minimum of fuss it may just make them move on to try the next vehicle. PN is BU5A-9C268-AB, First character definitely a "B"