If you haven't ever used a yubi before - it has the authenticator, which is the short fast press. But many people don't know you can also program the yubi to store a secondary phrase or passcode on the key itself. Once stored a LONG press will spit out the stored digits.

I would store my entire master password on it - but if somebody steals say my laptop - they now have access to my MP. Where the yubi only has half and I type the other half in. So that means the yubi key half that is stored can be a very strong set of digits/characters. And I can swap them out where yubi is the first part of the password - or I enter the part I know and yubi is the last part.