He may star on "Mad Men," but Vincent Kartheiser sure knows how to make his fiancee very happy.

Just look at that rock!

Ever since he got engaged to "Gilmore Girls" star Alexis Bledel earlier this year, we've been dying to see the engagement ring ... and last night, she finally showed it off!

Vincent reportedly picked out the giant sparkler himself and popped the question after about a year of dating.

Bledel tells Us Weekly that the two haven't started planning the wedding just yet -- but adds that they will be "doing it together."


See how her ring stacks up against other celebrity rocks in the gallery above.

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