Do NOT buy Google Titan Security Key
Google is now selling its Titan security key and it's a good thing to make people know about U2F and FIDO and I encourage everyone to have that kind of devices. But don't buy them from Google.
Why? Because Google ones are not made by Google but by Feitian and the Google Titan Security Key Bundle will cost you 50 $ while you can buy a similar security key bundle from Feitian for 40 $. No need to give more money to the greedy Google company.