What piping tip can I use to make BIG swirls on cupcakes?

I just watched cupcake wars and I was wondering what kind of piping tip do they use to make the swirls so big? Because I have a round wilton piping tip, but it makes very small round swirls. If anyone knows what size tip this is please let me know. Thank you in advance! (I hope this made sense)
Update: big swirls like this http://farm4.static.flickr.com/3005/3086495244_40c767e20f.jpg
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