How do you change the Text Size?

I mean in GUIs.

Heres what I tried.

local Example = Instance.new("TextLabel")
Example.Parent = ScreenGUI
Example.Text = "Hello!"
Example.TextSize = 18

Please Help!

local Example = Instance.new("TextLabel")
Example.Parent = ScreenGUI
Example.Text = "Hello!"
Example.FontSize = Enum.FontSize.Size18 

Here you go!

This links can help:------------------------------------------------------------------------------------------ http://wiki.roblox.com/index.php?title=API:Class/TextButton/FontSize http://wiki.roblox.com/index.php?title=Enum