In One Piece, Color of Arms Haki, also known as Armament Haki, is arguably the most useful form of this power; these are the best users. Source: Internet
He has an advanced mastery in all three types of Haki and kickass devil fruit -- one that is more than enough to take down Coby. Source: Internet
He has continuously worked on his Haki as well as his devil fruit ability. Source: Internet
That being said though, the fruit would be capable of much more if Haki -both Armament and Observational- were added to the equation. Source: Internet
Those who have trained their Armament Haki to the very peak can use a type that fans call Advanced Emission of Haki. Source: Internet